Deadly explosions struck a Damascus district housing members of Syrian President Bashar al-Assad's Alawi sect live and gunmen killed the brother of the speaker of parliament, as violence escalated in the capital.
Britain suggested offering Assad immunity from prosecution as a way of persuading him to leave power. The opposition said at least 100 more people were killed in the 19-month old revolt.
"Anything, anything, to get that man out of the country and to have a safe transition in Syria," British Prime Minister David Cameron told Al-Arabiya news network in Abu Dhabi before flying to Saudi Arabia.
Syrian state media said at least 10 people were killed and 30 wounded by a deadly explosion in the Hai al-Wuroud district in the northwest of the capital.
The hilltop neighborhood is situated near a barracks and housing for elite army units, and is home to members of Assad's Alawi sect, an offshoot of Shia Islam. Syria's rebellion in is drawn mainly from the Sunni Muslim majority.
Opposition activists said three explosions were heard in Hai al-Wuroud and at least 15 people killed. A car bomb exploded near a shopping mall in the mixed neighborhood of Ibn al-Nafis, killing and injuring several people, they said.
Officials and their families are increasingly being targeted by assassins as violence spreads in the capital. Victims have included parliamentarians, ruling Baath party officials, and even actors and doctors seen as Assad supporters.
State television said gunmen had assassinated Mohammed Osama al-Laham, brother of the speaker of parliament, in Damascus's Midan district. No group claimed immediate responsibility.
Peace envoy Lakhdar Brahimi warned that Syria, where some 32,000 people have died in 19 months of violence, could end up a collapsed state like Somalia, prey to warlords and militias.
Opposition factions were meeting in Qatar in an effort to forge a common front. The opposition has remained divided between Islamists and secularists; civilians and armed fighters; and exiles and those working inside the country.
More than 100 people were killed across the country on Tuesday, said the Syrian Observatory for Human Rights, a pro-opposition body based in Britain that compiles activist reports.
Air strikes killed 17 people, including women and children, in the Damascus suburb of Kfar Batna, it said. Video footage of the raid's aftermath posted on the Internet, which could not be verified, showed a toddler with a severed head and the torso of a young man, his head and limbs gathered near him by rescuers.
Insurgents killed 12 soldiers and wounded 20 in an attack on a convoy of off-road vehicles in the northern province of Idlib.
Air strikes and artillery barrages unleashed by the Syrian military in the last few weeks have devastated whole districts of the capital, as well as parts of towns and cities elsewhere.
Yet, for all their firepower, Assad's forces seem no closer to crushing their lightly armed opponents, who in turn have so far proved unable to topple the Syrian leader.
"Of course I would favor him facing the full force of international law and justice for what he's done," Cameron said of Assad. "I am certainly not offering him an exit plan to Britain. But if he wants to leave he could leave, that could be arranged."
It was unclear if Cameron had spoken to other UN Security Council members about the idea — which could involve offering Assad immunity from prosecution if he accepted asylum in a third country. Nor was it clear what nation would take him.
The UN human rights office has said Syrian officials suspected of committing or ordering crimes against humanity should face prosecution at the International Criminal Court.
UN investigators have been gathering evidence of atrocities committed by rebels as well as by Assad loyalists.
Brahimi, the UN-Arab League envoy to Syria, told the London-based Al-Hayat newspaper he did not expect ethnic or sectarian partition there. "What I am afraid of is worse ... the collapse of the state and that Syria turns into a new Somalia."
At the United Nations, diplomats cited a senior UN official as telling the Security Council that Brahimi had urged Russia to be "more pro-active" in resolving the Syrian crisis.
In a closed-door session of the 15-nation council, UN political affairs chief Jeffrey Feltman also said he had received credible reports of the use of cluster bombs by Syrian government forces, the envoys reported.
Human rights groups have reported in the past that Syria used cluster munitions. Such weapons, which spread bomblets that explode over an area, are banned by most countries, but Syria — like the United States, Russia and China — has not signed up to the treaty outlawing them. Regardless, rights groups consider their use in areas populated by civilians to be a war crime.
Big powers and regional nations are split over Syria. Russia and China have blocked three Western-backed UN Security Council draft resolutions aimed at exerting pressure on Assad.
Brahimi, speaking in Cairo on Sunday, called on the council to adopt a resolution based on an understanding brokered by his predecessor Kofi Annan in Geneva in June which called for the establishment of a transitional government in Syria.
Russian Foreign Minister Sergei Lavrov urged the Syrian opposition to enter talks with the authorities to end the crisis and abandon a precondition that Assad step down.
"The most important thing is stopping the violence immediately. If it is more important to the other side to change the Assad regime, then they want to continue the bloodbath in Syria," Lavrov said in Amman after meeting former Syrian Prime Minister Riad Hijab, who defected to Jordan in August.
Hijab said Assad's removal was "the only way out."
Assad's foes have failed to unite, making it harder for the outside world to support or arm them.
Prominent dissident Riad Seif has proposed a new 50-member unity council, but the head of the widely criticized Syrian National Council (SNC), which is based abroad, said it should retain a "central role" in any opposition configuration.
A Doha-based diplomat said SNC members feared their group risked losing influence in the new civilian body, which would later choose an interim government and coordinate with armed rebel groups. Seif's initiative is to be debated on Thursday at the opposition meeting in Qatar.
Syria has accused Qatar, Saudi Arabia and Turkey, among others, of fuelling the bloodshed by backing the rebels.
The Syrian struggle has taken on a sectarian tone, with mostly Sunni rebels battling loyalist forces dominated by Assad's minority Alawi sect.
Saudi Arabia and other Sunni Gulf Arab states are wary of powerful Shia neighbor Iran, one of Assad's few allies.
In Turkey, fiercely critical of Assad, the state-run news agency reported the arrival overnight of seven Syrian army generals who had defected and crossed the border. Scores of Syrian officers have defected to Turkey during the uprising.