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The U.N.-Arab League envoy for Syria warned Tuesday that the country could become another Somalia — where al-Qaida-linked militants and warlords battled for decades after the ouster of a dictator — if the civil war is not ended soon.

Battles between regime forces and Syrian rebels left more than 140 people dead across Syria on Tuesday, while the brother of Syria's parliament speaker was gunned down in Damascus — the latest victim of a wave of assassinations targeting high-ranking supporters of President Bashar Assad's regime.

Among the dead were at least 13 people who died in a series of explosions in the capital Damascus, targeting impoverished districts of the capital. Dozens others were wounded, activists said.

The violence aroused new concern about the faltering diplomatic efforts to try to end the conflict, with the U.N. political chief warning that the Syria crisis risks "exploding outward" into Lebanon, Turkey and Israel.

Britain's prime minister offered the latest long shot — that Assad could be allowed safe passage out of the country if that would guarantee an end to the fighting.

But there has been no sign the embattled Syrian leader is willing to step down as part of a peaceful transition to save the country. Assad has vowed to militarily crush the nearly 20-month old rebellion against his rule, and aides say a new president will only be chosen in elections scheduled for 2014.

U.N.-Arab League envoy Lakhdar Brahimi, who, like his predecessor Kofi Annan has been unable to put an end to the conflict, warned the civil war could spiral into new levels of chaos.

"The situation in Syria is very dangerous," Brahimi said in remarks published Tuesday in the pan-Arab daily Al Hayat. "I believe that if the crisis is not solved ... there will be the danger of Somalization. It will mean the fall of the state, rise of warlords and militias."

Somalia has been mired in conflict for more than two decades after warlords overthrew the east African nation's longtime dictator in 1991 and then turned on each other. The government, backed by African Union troops, is currently battling Islamist extremist rebels linked to al-Qaida.

Syria, by comparison, has always had a strong central government, and despite losing large swathes of territory, the regime still maintains a grip on many parts of the country, including Damascus, the seat of Assad's power, where basic government services still function.

But if the regime collapses, the country could fast shatter along multiple fault lines, leading to protracted bloodshed.

The predominantly Sunni nation is a patchwork of religious and ethnic groups. The regime is led by Assad's Alawite minority, an offshoot of Shiite Islam, but there are also considerable Kurdish and Christian populations.

The conflict's already increasing sectarian overtones suggest any power vacuum could usher in renewed violence. Predominantly Kurdish areas in the north and Alawite majority areas in the central coastal mountains could spin away, and mixed areas — already hard hit by the conflict — could plunge further into conflict.

Dozens of opposition groups and rebel brigades have taken up the fight against Assad. But they share little common vision for the future and are divided by acute ideological differences, particularly among secularists and Islamists, and could easily turn on one another after Assad's fall.

There are also growing concerns over the injection of al-Qaida's influence into the country's civil war. Jabhat al-Nusra, a shadowy jihadi group with an al-Qaida-style ideology, has carried out numerous suicide bombings targeting regime and military facilities.

The U.S. and its Western allies have been reluctant to provide weapons to rebels fighting in Syria partly out of concern they could fall into the hands of extremists.

At the United Nations, Jeffrey D. Feltman, the U.N. undersecretary general for political affairs, warned that the escalating violence will lead Syria "to its destruction" and threatens neighboring Lebanon, Turkey and Israel.

"The situation inside Syria is turning grimmer every day, and the risk is growing that this crisis could explode outward into an already volatile region," he told a meeting the Security Council.

More than 36,000 people have perished in the fighting, according to activists, and the death toll rises daily.

On Tuesday, more than 140 people were killed in violence across the country, activists said, including in a series of airstrikes on rebel strongholds in the suburbs of Damascus. Among the dead were at least 13 people who died when three bombs exploded in the al-Wuroud district on the capital's northwestern edge, populated by members of Assad's Alawite sect. The blasts occurred near housing for the elite Republican Guard, which is led by Assad's brother Maher Assad.

A few hours later, a powerful car bomb exploded in a Sunni Muslim neighborhood of the capital, causing multiple casualties and massive destruction to nearby buildings, activists said. No further details were immediately available on casualties from the bomb in al-Qadam district, which was detonated near a mosque around 1 a.m. local time Wednesday.

The brother of Syria's parliament speaker was killed in a hail of bullets by gunmen who targeted him as he drove to work in Damascus. Mohammed Osama Laham, the brother of Speaker Jihad Laham, was the latest government supporter to be targeted for assassination.

Diplomacy has been deadlocked at the U.N., where Syria's allies Russia and China have repeatedly blocked attempts to approve harsher sanctions in the Security Council.

British Prime Minister David Cameron suggested Tuesday that Assad could be allowed safe passage out of the country if that would guarantee an end to the nation's civil war.

Asked in an interview with Al Arabiya television if he would contemplate offering Assad an exit route, Cameron said the international community would consider anything "to get that man out of the country and to have a safe transition in Syria."

In London, officials said Cameron was not suggesting Assad could escape potential international prosecution if he were to be granted passage out of Syria. They also said there were no talks aimed at crafting an exit deal.

Seven generals, meanwhile, fled into neighboring Turkey, the latest of dozens of top-ranking military officers to abandon the regime. The Turkish state news agency Anadolu said they arrived in the Turkish border province of Hatay seeking refuge. Their identities were not disclosed.

They join dozens of other generals who have abandoned the regime. More than 110,000 Syrians have sought refuge in Turkey since the uprising began in March 2011.

In Jordan, which also borders Syria, visiting Russian Foreign Minister Sergey Lavrov met with Riad Hijab, the former Syrian prime minister who defected to Jordan in August. It was a rare high-level contact between Moscow and a Syrian opposition figure.

Lavrov said the talks were meant to get firsthand information from the Syrian opposition on how they view a solution to the civil war. "The idea of the meeting was to get an agreement or a roadmap on how to deal with opposition forces and save the Syrian people," Lavrov told reporters.

Activists and state media reported clashes, shelling and air raids across Syria, including in Houla in central Syria, Saraqeb in northern Idlib province and Kfar Batna, a Damascus suburb.

Activists posted videos online that showed scenes of death and destruction in Kfar Batna. In one, a group of people frantically shout as they search the rubble of a building, removing a slab of cement to reveal the body of a young girl. In another, a dead or wounded man is seen lying on the back of a pickup truck surrounded by smoke, fire and destroyed cars and buildings. The videos appear to be consistent with AP reporting on the airstrikes in suburbs of the capital.

Meanwhile, in the Gaza Strip, a spokesman for the Palestinian group Hamas, Ayman Taha, said the Syrian government had sealed its offices in Damascus, finalizing the break between the Islamic militant group and its former patron after Hamas switched sides to support the armed rebellion against Assad's regime.

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Associated Press writers Dale Gavlak in Amman, Suzan Fraser in Ankara, David Stringer in London and Abdullah al-Shihri in Riyadh, Saudi Arabia, contributed to this report.