Bombings, clashes and air strikes shook Syria on Tuesday as British Prime Minister David Cameron said he would back giving safe passage to President Bashar al-Assad if it meant ending the bloodshed.

In the latest in a wave of bomb attacks, at least 10 civilians were killed and 40 wounded as three blasts hit the west Damascus suburb of Qudsaya on Tuesday, the Syrian Observatory for Human Rights said.

As fighting elsewhere claimed more lives, Cameron told Al-Arabiya television he wanted Assad to be held to account for his crimes but that his departure could be arranged.

Asked what he would say if Assad asked for a safe exit, Cameron told the UAE-based channel: "Done. Anything, anything to get that man out of the country and to have a safe transition in Syria.

"Of course, I would favour him facing the full force of international law and justice for what he's done," said Cameron, who is on a tour of the Middle East.

"I am certainly not offering him an exit plan to Britain but if wants to leave, he could leave. That could be arranged."

The Observatory said at least 131 people had been killed nationwide on Tuesday, as air strikes hit targets around the country and fighting raged around Damascus, in the second city Aleppo and in the northwestern Idlib province, where rebel forces killed at least 12 troops in an ambush.

Warplanes carried out four bombing raids on the Idlib town of Saraqeb, killing 19 civilians and wounding 62, the Britain-based watchdog said.

Video footage posted by activists, which could not be independently verified, showed survivors huddled amid the rubble of buildings as a warplane dropped bombs strapped to parachutes.

The Observatory said 247 people were killed on Monday, in the deadliest day in Syria since an attempt to impose a ceasefire for the October 26-29 Eid al-Adha Muslim holiday collapsed.

An Israeli patrol was hit by gunfire in the buffer zone between the two countries on the Golan Heights on Monday, and Israeli ambassador to the United Nations Ron Prosor said his government viewed heightened tensions with Syria with the "utmost concern."

The UN condemned the fighting by Syrian forces close to the ceasefire line.

"It has the potential to escalate tensions between Israel and Syria and jeopardises the ceasefire between the two countries and the stability of the region," UN spokesman Martin Nesirky said.

The UN's top political official, Jeffrey Feltman, told the Security Council there was credible evidence that the army is using banned cluster bombs and that violence had worsened since UN-Arab League peace envoy Lahkdar Brahimi's abortive ceasefire attempt last month.

Brahimi said he feared the "Somalia-isation" of Syria.

"Some are talking of the danger of seeing Syria divided... I think the real risk is not partition but 'Somalia-isation', with the collapse of the state and the emergence of militia and armed factions," Brahimi said in an interview with the Al-Hayat newspaper.

Britain's UN ambassador, Mark Lyall Grant, told reporters the Security Council hoped for a briefing from Brahimi before the end of the month on his efforts to start political talks.

Britain and other European governments "believe it is long past the time" when the Security Council just passes statements and resolutions with no coercive element, he said.

The Observatory says more than 36,000 people have died since the uprising against Assad's rule broke out in March 2011, first as a protest movement inspired by the Arab Spring and then as an armed rebellion.

The exiled opposition Syrian National Council, which backs the rebels, met in Qatar under intense US pressure to reform.

Its leader, Abdel Basset Sayda, insisted the bloc must remain the "cornerstone" of the Syrian opposition, rejecting US accusations it is unrepresentative.

Opposition figures were to discuss an initiative by leading dissident Riad Seif, reportedly backed by the United States, to broaden the opposition beyond the SNC and form a government-in-exile.

International efforts to halt the violence have been frustrated by disagreements, with Russia and China blocking attempts by Western and Arab governments to put more pressure on Assad.

Moscow has accused Western governments of conniving in the delivery of weapons to the rebels by Gulf Arab states, and Russian Foreign Minister Sergei Lavrov said on Tuesday that the rebels had acquired 50 Stinger shoulder-fired missiles.

Speaking after talks in neighbouring Jordan, Lavrov said the missiles were in no way "intended for defence" and could be used to target regime aircraft or civilian planes.

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