The Syrian army fought armed opposition groups in the suburbs of Damascus on Monday, gaining ground once held by rebels and highlighting the increasingly violent nature of the struggle.

The army regained control of some neighbourhoods where rebels had established a presence in recent weeks, killing at least 15 people in the process, opposition activists told Reuters. More than 200 people, including both civilians and regime and opposition fighters, are estimated to have been killed across the country since Thursday.

“Tanks have gone in but they do not know where the Free Syrian Army is,” said Maher al-Naimi of the FSA, by phone from Turkey. “We are still operating close to Damascus.”

Regime forces also shelled the rebellious central city of Homs on Monday, according to activists, with heavy machine gun fire reported in the Baba Amr district, which has become a stronghold of armed opposition. Activists reported that at least 14 were killed in the city on Monday.

The government of Bashar al-Assad, the president, has intensified its battle against army defectors and opposition protesters since the Arab League observer mission – which was to monitor Damascus’s compliance with an undertaking given in November to end violence – suspended its operations on Saturday, citing “the critical deterioration of the situation in Syria and the continued use of violence.”

The fighting came as Arab and western diplomats prepared to meet at the United Nations Security Council to discuss a draft resolution backing the Arab League proposal calling on President Bashar al-Assad to step aside.

Faced with a crackdown on dissent that the UN estimates has claimed more than 5,400 lives, opponents of the regime, many claiming to be affiliated with a loosely organised group of soldiers who have defected and others calling themselves the Free Syrian Army, have resorted to arms.

On Monday, activists reported that defected soldiers freed five imprisoned comrades in an assault on a military base in the northwestern province of Idlib, while outside the city of Hama, they were reported to have attacked a large military checkpoint, destroying several transport trucks.

State media also reported that an ”armed terrorist group” blew up a gas pipeline at dawn Monday. The pipeline carries gas from the central province of Homs to an area near the border with Lebanon. SANA news agency reported that the blast happened in Tal Hosh, which is about 8km from Talkalakh, along the border with Lebanon.

Damascus has consistently blamed the uprising in Syria on terrorists. A government official was quoted on Syrian television as saying the Arab League’s proposal for Mr Assad to hand over power would put pressure on the Security Council “with the aim of calling for foreign intervention and encouraging armed groups to increase violence”.

Reporting by Abigail Fielding-Smith in Beirut and Michael Peel and Tom Gara in Abu Dhabi

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