Three years since the start of the uprising, nine million people have been displaced by fighting.
David Cameron, the British prime minister, has said he will support granting President Bashar al-Assad a safe passage out of Syria to help end the civil war.
Cameron made the comments on Tuesday in a television interview while visiting the United Arab Emirates before flying to Saudi Arabia.
He said “anything” should be done to help “get the 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. I am certainly not offering him an exit plan to Britain, but if he wants to leave he could leave, that could be arranged,” he told Al Arabiya.
The news came as the UN-Arab League envoy for Syria, Lakhdar Brahimi, warned Syria could become another Somalia if the conflict is not ended soon.
Meanwhile, battles between government forces and rebels continued on the ground, with opposition activists reporting 140 deaths on Tuesday.
Bombs exploded in several districts of the capital, Damascus, and the state news agency said gunmen killed the brother of the parliament speaker while he drove to work in the city.
Mohammed Osama Laham, brother of Jihad Laham, was killed in the Damascus neighbourhood of Midan, SANA reported.
The attack was the latest in a wave of assassinations targeting Syrian officials, army officers and other prominent supporters of Assad’s regime.
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Four of the president’s top security aides were killed in a bombing of state security headquarters in Damascus on July 18.
State media also said at least 10 people were killed and 30 wounded by an explosion in the Hai al-Wuroud district in the
northwest of the capital on Tuesday.
The hilltop neighbourhood is situated near a barracks and housing for elite army units, and is home to many Alawites, belonging to the same Muslim sect as Assad.
In comments that underlined the gravity of the situation in Syria, peace envoy Brahimi said what is happening is a ”big catastrophe”.
He told the pan-Arab daily Al Hayat that international efforts now are focused on getting a “binding resolution by the [UN] Security Council” to start a political process that will lead to change.
“I don’t want to go too far in pessimism, but the situation in Syria is very dangerous. The Syrian people are suffering a lot,” Brahimi said.
“I believe that if the crisis is not solved in a right way, there will be the danger of Somalisation. It will mean the fall of the state, rise of war lords and militias.”
Also on Tuesday, Sergei Lavrov, the Russian foreign minister, urged the Syrian opposition to abandon its precondition that Assad step down before any talks can be held on ending the conflict.
Speaking after meeting former Syrian Prime Minister Riad Hijab, who defected to Jordan last August, Lavrov accused the opposition of disregarding Syrian lives by demanding the immediate removal of Assad.
“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.
Lavrov was rebuffed by Hijab, who said Assad’s removal was “the only way out” for there to be a negotiated settlement to the 19-month-old conflict.
After the meeting, Hijab told Al Jazeera: “We left the meeting in disagreement. There will be no negotiations while Bashar al-Assad and Syrian officials with blood on their hands are still in power.”
The meeting with Russia happened while the opposition Syrian National Council, meeting in Qatar to broaden its membership, said on Tuesday that the “cornerstone” umbrella group should preserve its leading role in any revamp.
Abdulbaset Sieda, head of the SNC, also denounced the failure of the international community to act to end “massacres” being committed by forces loyal to Assad.
His remarks were made during a meeting of the SNC general assembly in Qatar’s capital Doha, as the United States heaped pressure on the opposition to form a wider structure.
Sieda said the SNC would take part in a broad opposition meeting on Thursday called by host Qatar and the Arab League, but insisted on a leading role for the council.
“We will attend the meeting with an open heart and mind. But we would like to stress from the start the need to keep the SNC as the cornerstone of the Syrian opposition,” said the SNC chairman.
“We think that any attempt to target the SNC, whether intentionally or not, will prolong the crisis,” he added.