Four men involved in the attempted second wave of terrorist attacks in London two years ago were convicted on Monday of conspiracy to murder.

Muktar Said Ibrahim, Ramzi Mohamed, Yasin Omar and Hussain Osman were found guilty at Woolwich Crown Court after a trial lasting almost six months. The jury is still considering its verdicts in respect of two other individuals.

Prosecutors have alleged that all six defendants were part of an “extremist Muslim plot” to detonate homemade bombs on three Tube trains and a bus two weeks after the July 7 2005 attacks on London's public transport system had killed more than 50 people.

Prosecution lawyers have claimed that the July 21 2005 plot failed because the chemicals in the rucksack-borne devices – which used hydrogen peroxide and chapati flour – proved less concentrated than the men believed. This, they have argued, was simply fortuitous and was not because of any deliberate action on the part of the defendants.

Most of those convicted on Monday maintained the devices were intended as a hoax. Mr Ibrahim, who was born in Eritrea, claimed to have tested the mixture. The bombs, he contended, were meant to be a “protest” designed to cause chaos on the transport network, but he was not on a suicide mission.

Mr Osman, meanwhile, claimed to have been bullied into making the bombs.

In the chaotic aftermath on July 21, Mr Omar escaped to Birmingham, wearing his mother-in-law's burqa, where he was arrested by police. Mr Mohammed and Mr Ibrahim were cornered in a flat in west London, where they were arrested by armed officers after being forced on to a balcony in their underwear – the whole scene being filmed by TV cameras.

The dramatic moment when Mr Mohamed attempted to detonate his device on a Tube train was captured on CCTV. The footage showed the defendant turning the rucksack that contained the homemade bomb towards one of the passengers and her nine-month-old son.

Afterwards, as passengers fled in panic, an off-duty fireman was seen gesturing to Mr Mohamed. The fireman told jurors that he remembered shouting: “What have you done?” Mr Mohamed, he said, replied “What's the matter? It's bread. It wasn't me, it was that,” as he looked at the rucksack.

The remaining defendants are Manfo Kwaku Asiedu and Adel Yahya. Mr Justice Fulford, overseeing the trial, has told jurors he will accept majority verdicts.

Monday's guilty verdicts are the latest of a series of convictions in high-profile terrorism-related trials.