A woman dries cassava in the heat from Shell waste gas flares

As our speedboat casts off from Yenagoa, in the heart of the Niger Delta, I feel as if I am being propelled into a more welcoming world. A bracing wind replaces the humid closeness of the town, a monument to disorder clustered around a single, thunderous main road. The foliage on either side of the water is thick and lush, with oil palms peeping over the top of the tree line. The river traffic – mainly canoes loaded with goods such as fish, wood and plantains – clings to the banks to avoid being capsized by our wake.

I am travelling with a few guides and a fellow journalist, Glenn ­McKenzie, in search of the Niger Delta’s main militant movement: the Movement for the Emancipation of the Niger Delta, or Mend. The organisation had attacked oil installations and kidnapped dozens of oil workers, prompting the big companies to send non-essential staff home and shut down hundreds of thousands of barrels a day of production.

Members of Mend. The white flag signifies the Ijaw god, Egbesu

Soon we pass a village where a long white flag flutters from a post. It’s a symbol of Egbesu, a water spirit central to the culture of the Ijaw people, the largest ethnic group in the region. Simeon, one of the guides, explains that white flags represent peace; red, fighting spirit. If you are killed in battle, it means not that Egbesu has failed you, but that you have violated its laws. As Simeon puts it bluntly, “You oppress, you steal, you will die.”

For the western oil majors, long used to a bit of heat, the security crisis was as bad as they had known. By this summer, estimates of Nigerian ­production ranged from 1.6 million barrels a day to as low as 800,000 barrels a day, all far distant from the 4 million barrels-a-day target for 2010. In July, an increasingly desperate government announced a two-month amnesty in an effort to tempt the militants out of the creeks. Mend has since threatened to resume hostilities from September 15.

It all reminded me of a similar amnesty five years earlier, when I’d first started to chart the Delta militancy that now rivals scam e-mails as the phenomenon most defining Nigeria in the eyes of the world. Then, as the FT’s west Africa correspondent, I’d been awoken to the dark story of ­Nigerian oil through a series of encounters with a flamboyant militant leader known as Alhaji Mujahid Dokubo-Asari. In 2004, he’d sent tremors through world oil markets after his threat to launch an attack known as “Operation Locust Feast” against industry installations in the Delta. His activities – abruptly curtailed when he was imprisoned for alleged treason – helped propel the world oil price above $50 for the first time.

The Delta’s torments – pollution, corruption and widespread poverty, despite decades of oil exports worth hundreds of billions of dollars – had continued to multiply since 1995, the year that the execution of Ken Saro Wiwa and eight other activists first brought the region to the world’s attention. The situation had grown more venal, more violent and more desperate. Foreign oil interests were now being confounded by the turmoil that their own behaviour over decades had helped create.

. . .

A Nigerian army river patrol

About an hour from Bayelsa, the boat’s engine is suddenly cut. Our guides all raise their hands in the air, prompting Glenn and me to follow suit. We are approaching a checkpoint of the Mobile Police: they are notoriously trigger-happy and are likely to be especially skittish at this volatile time. Two officers beckon us to a jetty, from where we clamber up to meet them. Glenn and I are asked a series of questions: is the state government aware of our visit? Where is our security? What did we think about the 2007 national elections held the previous week? We evade and lie, saying we have all the permissions. They seem satisfied. The whole process has a half-hearted feel, as if the officers’ main purpose is to cover their backs should anything happen to us.

After a ride of another hour or so, the weather begins to change for the worse. The wind strengthens and it starts to spot with rain. A speedboat appears from a tributary to our left and zips across our course. Looking to our right, we see other signs of life: a line of men on the bank, all naked. About 15 of them are waiting to go into the water, where half-a-dozen ­others are already splashing around. They are all Mend fighters.

The speedboat pulls up alongside us and a young man greets our guides. One of them, Godson, produces a bottle of Chelsea gin, from which he has been taking nips during our journey. Our visitor takes a swig, then sprays the gin to the left of our boat’s stern, as if in blessing. The new man introduces himself to us as Mend commander Timi ­Freeman, although his dress seems more suited to a day on the golf course than a militia war. He wears a visor and a mauve-and-white Breton-style striped top. Instead of a string of onions round his neck, he’s got a Nokia headset.

Freeman – “Fineboy” to the others – is a youthful 30, his face still round with baby fat. He tells us we are now in a zone under the total control of Mend; the government soldiers garrisoned in the area dare not approach. “They fear,” he says. “We don’t look for trouble. But if the military happens to come here, they are looking for trouble.”

Under Freeman’s guidance, we change course and take a sharp left down another branch of the river. Some minutes later, we moor at the ­village of Korokorose, where the children welcome us by breaking into a ­chorus of “Oyinbo Pepe!”, a favourite greeting for white foreigners.

A young man carrying a rifle leads us to a half-built house opposite a field of tall grass, where we are asked to wait for a Mend field marshal. When he arrives, he sits across from us, his face half-obscured by his hat. He listens to Simeon’s introduction and then offers us a drink. I take a non-alcoholic malt; many of the young men take Star beer. We sit and wait for the field marshal to speak, but he is as taciturn as he is hospitable. Soon he gets up to go. We are told we will see him again later, but we never do.

It’s becoming clear that we will have little say in determining the course of the day’s events. We go back to the boat and are whisked away to a ­village called Ikebiri I. There, we wait again, this time in the darkened room of a dilapidated house, the dried mud on its walls crumbling away. Outside, a crowd gathers despite the rain. Children seem to be spilling in through every door and window.

Slum dwelling in Lagos, a city built on oil wealth

Eventually, an older man enters the room. After introducing himself as Francis Ododo, he launches into an account of how militancy in the Delta is fuelled by the people’s feeling that they have been robbed. He attacks Olusegun Obasanjo, the former military leader who ruled as civilian ­president between 1999 and 2007, over Obasanjo’s 1978 Land Use Act, which gave the federal government ownership of the region’s oil. “Now the Niger Delta man has seen that he is nowhere,” Ododo rages. “And that’s why any problem that you are seeing today is happening.”

The result, Ododo says, is that many long-standing oil-producing ­communities such as Ikebiri I are becoming increasingly restive. People are unhappy because Chevron, which operates in the area, still flares its waste gas, causing acid rain and polluting the area with night-time light. ­Chevron doesn’t employ enough local people, and neither it nor the government have brought development: petrol in Ikebiri I, a prime source of oil, costs 150 naira a litre (60p), or more than twice the going rate elsewhere. There are no roads linking Ikebiri I to the main cities, so a trip to Yenagoa costs a prohibitive £10 return. Ododo talks about how Niger Delta youths have been “pushed to the wall”.

. . .

En route to our next stop, Freeman and I chat about his life, which has been shaped since his teenage years by conflict. He has been involved in four militant organisations since leaving school in 1994, including Asari’s Niger Delta People’s Volunteer Force. I notice two scars on his hand – one long, the other in the shape of a cross. He says they were caused by a soldier’s machete.

In 1999, Freeman says he was sent to prison after a shootout in which the ­military killed two of his men and he killed a soldier. He was held for five years without trial, and decided to rejoin the militants on his release. None of the underlying injustices he was fighting against have changed, he claims. “I became a militant because of the spoiling of my people. We have oil but no development. That is why I have said I will fight until my last bullet – until whoever will kill me.”

When I ask him if he has a family, he smiles and replies that he has a mother and father. Is he married? No, he replies. Would he like to get married? He smiles charmingly, gives me a thumbs-up sign and says, “Yes”. I say that it must be difficult to find a wife when he leads the kind of life he does. He shrugs and says he sees no choice. We fall silent, and after a short time he gently taps me on the arm. “Before you marry,” he says, “you have money. I have no money. If I have money, I will marry.”

2006, Mend activists prepare to release Macon Hawkins, a US oil worker they had been holding hostage

Freeman says his territory consists of three camps, each of which house between 100 and 200 men at any one time. The militants are armed with rifles, light and heavy machine guns, and even two rocket-propelled ­grenade launchers. One of these they bought, the other they seized from government soldiers. Asked who supplies the weapons, he laughs, a little coyly. “We buy them from the military.” Sometimes arms come from neighbouring Cameroon, he says, sometimes from countries further afield, such as ­Liberia. He claims that the weapons dealer they regularly use even has a supply line from Iraq. Asked where the men get the money to buy the arms, he pauses, weighing up how much to tell me. He finally replies that the militants take oil from the pipelines and sell it on the black market. They finance themselves by exploiting the very industry that has blighted their region for half a century.

By now, we have travelled to the very limits of the Niger Delta, where the river meets the sea. In front of us, through a gap in the sandbanks, I can see the waves of the open ocean. Further still, I can see the gas flare of an offshore oil field.

We veer away from the sea’s jaws and put in at the village of Kuluama I, another area where Chevron operates. As ever, the local leaders are ready with their case against the oil industry. Emmanuel Orumo, chairman of the Community Development Council, tells us that there are hundreds of jobless youths denied work by Chevron and then kept at bay by “uniformed men”. “We have graduates who go for interview,” Orumo says, adding that the company fails the community “woefully”.

The multinational has declined to answer questions I put to it about the complaints in Kuluama I and Ikebiri I.

We climb onboard the boat again to be taken to Kuluama I’s most alarming sight of all. A few minutes’ ride away is a sandbar where blackened mangrove roots twist as if in silent agony. A thin layer of seawater rushes in and out over the sand in rhythm with the waves. The encroachment of the sea, villagers tell us, is becoming greater and greater and will eventually wash the community away. They blame the problem on seismic activity by oil companies such as Chevron, whose offshore platforms are visible in the distance. It could equally be global warming, itself indirectly attributable to the global oil industry.

People’s fear and anger at this apocalyptic prospect is visible and ­genuine. Reuben Wilson Clifford, a local man, holds his arm in the air like a weapon, and promises destruction if the village is indeed washed away. Someone else shouts out: “We will carry the gun to claim our rights. Since we have nothing – nobody cares for us.” It is an eerie echo of a conversation I’d had the previous week with an oil executive: he said the level of violence that had developed in the Delta was not surprising, as people there had nothing to lose.

Whatever the cause of the sandbar flooding, there is something unsettling about this place where young men rage under the oil industry’s ­distant and baleful gaze. As we stand surrounded by the withered plant roots, the sand sucks in my boots and an incoming wave submerges them. ­Leaving, we pass houses on stilts surrounded by water, ready to be taken by the flood, if and when it comes.

. . .

Dusk is looming, and it is too late for us to go back to Yenagoa. Glenn and I decide to take up the militants’ offer to stay the night, although we don’t know where we are going or where we will sleep. We have long since lost control of this trip, if we ever had it in the first place. After a breakneck ride back along the main waterway, we plunge into the mangroves. The creeks here are narrow and claustrophobic. I can hear cicadas and then, more and more clearly, drumming and chanting. Godson tells me not to be afraid, as we are in the Lord’s hands.

Ahead, two men with guns are perching in the mangroves, their faces part-covered with cloths. The boat stops next to them. Godson starts ­taking his trousers off, and Glenn and I are told to do the same. Then Godson and our fellow passengers step out of the boat one by one and into the deep creek water. They do not sink, and I see they are stepping on a cat’s cradle of mangrove roots that lies beneath the surface.

A militant prepares for combat with a voodoo ritual

By the time my turn comes, I feel close to passing out through a combination of nerves and hunger. I start to creep, slip and grasp my way towards the shore, willing myself to control my fear. Eventually, the riverbed becomes shallow enough to walk on. We wade in line to dry land, where a man is waiting with a blessing. As each of us passes, he flicks water at us, then sprinkles a white solution known as native chalk from a bowl he carries at his side. “You are holy!” he exclaims as he finishes.

A few yards back from the shore, there are about 20 men dancing to the beat of drummers, one of whom strikes an old car exhaust with a stick. As we walk towards them, I have a strange sensation of being simultaneously the centre of attention and completely ignored. All around, the air is pungent with hashish and incense.

I look round at the other dancing militants, whose appearance blends the whimsical, the spiritual and the surreal. Many are in their boxer shorts; some of these bear Tommy Hilfiger labels, while one pair is decorated incongruously with pictures of babies and flowers. Some of the men wear white or red cloths round their faces, and one has a white sheet on his head with holes for the eyes, like a fancy-dress ghost.

Our travelling companions immediately join in the dance, as caught up in the rhythm as they had been in discussions of Delta politics earlier in the day. Standing a foot or so away from me, one man shouts that his men are going to continue to capture white people like me. He could tie me to a tree now, shoot at me and no bullet would enter, he says, because I have just been blessed with the spirit of Egbesu. He grabs my arm urgently. “We are jobless,” he says. “The best way is to catch you people, flog you. That is the way we live.”

In the confusion, someone shepherds Glenn and me towards a small man with a white cloth around his face. He says he is called Commander Three Lions. He gives a rapid-fire talk about the history of the Delta, going back to the days of the ruthless Royal Niger Company set up under British rule, but the speed of his speech and the noise around us makes it hard to make out much of what he is saying. My notes on the conversation read like a stream of consciousness, perhaps mine as much as his:

The whole Nigeria … the criminal governance … there is nobody can take our oil … I fight Nigerian government … I am prepared for death … you ­people go back and tell them … we are not fighting for resources now … we are fighting for our lives.

As Three Lions speaks, two of the dancers hold up a large white cloth. A third man steps a few feet back from it, takes aim at it with his rifle and fires, making me jump. There is a cheer, and the two men holding the cloth raise it to show that it is unmarked by a bullet hole. It has Egbesu’s blessing. Later, I wonder how he did it. He could hardly have shot a live round into the crowd of dancers, yet if he had knowingly loaded a blank he would have been acknowledging that the Egbesu magic didn’t work.

Encouraged by the militants, Glenn and I briefly and nervously join in the dancing. And then, as suddenly as we were propelled into this world, we are told we should leave. We scramble back across the mangroves. “It seems easier on the way back,” I say, seconds before slipping and almost plunging into the creek. No doubt Egbesu is punishing me for complacency.

As we glide from the secret gathering, Freeman reflects on our encounter. His concluding comment seems to echo the precariousness of the entire Delta region and the sense of apocalypse just avoided – for now.

“They wanted to tie you with one cloth and shoot you,” he tells me. “But I told them not to.”

Michael Peel is the FT’s legal correspondent. This is an edited extract from ‘A Swamp Full of Dollars: Pipelines and Paramilitaries at Nigeria’s Oil Frontier’, published by I.B. Tauris. The book has been longlisted for The Guardian First Book Award 2009. To buy it for £14.39, plus £2.45 P&P, call the FT ordering service on 0870 429 5884 or visit www.ft.com/bookshop.

FT review of Michael Peel’s book