BEIRUT — The Arab League halted its observer mission in Syria on Saturday because of escalating violence that killed nearly 100 people the past three days, as pro-Assad forces battled dissident soldiers in a belt of suburbs on the eastern edge of Damascus in the most intense fighting yet so close to the capital.

The rising bloodshed has added urgency to new attempts by Arab and Western countries to find a resolution to the 10 months of violence that according to the United Nations has killed at least 5,400 people as Assad seeks to crush persistent protests demanding an end to his rule.

The United Nations is holding talks on a new resolution on Syria and next week will discuss an Arab peace plan aimed at ending the crisis. But the initiatives face two major obstacles: Damascus' rejection of an Arab peace plan which it says impinges on its sovereignty, and Russia's willingness to use its U.N. Security Council veto to protect Syria from sanctions.

Syria's Interior Minister Mohammed Shaar vowed the crackdown would go on, telling families of security members killed in the past months that security forces "will continue their struggle to clean Syria's soil of the outlaws."

Government forces launched a heavy assault on a string of suburbs and villages on the eastern outskirts of Damascus, aiming to uproot protesters and dissident soldiers who have joined the opposition, activists said.

Troops in tanks and armoured personnel carriers attacked the suburbs of Kfar Batna, Saqba, Jisreen and Arbeen, the closest of which lie only a few miles from downtown Damascus, said the Local Coordination Committees activist network and the British-based Syrian Observatory for Human Rights. Dissident troops were fighting back against the attackers, they said.

In a nearby suburb, Douma, gunmen ambushed a bus carrying army officers, the state-run news agency SANA, calling the attackers "terrorists." It said seven officers were killed.

The assault in the suburbs seemed to be a sign of the growing presence of dissident soldiers closer to the capital. Although the tightly controlled Damascus has been relatively quiet since the uprising began, its outskirts have witnessed intense anti-regime protests and army defectors have become more visible and active in the past few months.

"The fighting today is the most intense near the capital since the uprising began," said Rami Abdul-Rahman who heads the Observatory for Human Rights. "The Syrian regime is trying to finish the uprising militarily now that the case is being taken to the United Nations."

In Saqba, electricity and phone lines were cut off and mosque loudspeakers told residents to say in lower floors for fear high buildings might get hit in the fighting, said Omar Hamza, an activist in the district. "Random shelling and sound of explosions terrified the people," he told The Associated Press.

He said army defectors had managed to stop the advancing troops. The regime forces are putting all their force to finish the Free Syrian Army and protesters in the Damascus suburbs," Hamza said.

The Free Syrian Army force of anti-regime military defectors is based in Turkey, and its fighters frequently try to cross into Syria through the mountainous border area in the northwest. SANA reported that Syrian troops prevented gunmen from crossing in from Turkey on Saturday in fighting that it said left many of the infiltrators killed or wounded.

The LCC and the Observatory also reported intense fighting between troops and defectors in the town of Rastan near the restive central city of Homs.

The Observatory said at least 36 people, were killed across the country Saturday, including 17 civilians, three defectors and 16 troops, while the LCC said 20 died, half of them in Homs province, which has been one of the areas hardest hit by government crackdowns. The new deaths come after two days of bloody turmoil killed at least 74 people, including small children.

In the eastern oil-rich province of Deir el-Zour, an oil pipeline took a direct hit and caught fire as government troops shelled a nearby town, the two groups also said, reporting at least one person dead. State media blamed "terrorists" in the attack.

The month-old Arab League observer mission in Syria had come under widespread criticism for failing to bring a halt to the regime's crackdown. Gulf states led by Saudi Arabia pulled out of the mission Tuesday, asking the U.N. Security Council to intervene.

Arab League Secretary-General Nabil Elaraby said in a statement that the organization decided to halt the observers' work immediately because of the increasing violence, until the League's council can meet to decide the mission's fate.

He sharply criticized Damascus for the spike in bloodshed, saying the regime has "resorted to escalating the military option in complete violation of (its) commitments" to end the crackdown, Elaraby said. He said the victims of the violence have been "innocent citizens," in an implicit rejection of Syria's claims that it is fighting "terrorists."

Syria's state-run news agency quoted an unnamed official saying Damascus "regrets and is surprised" by the Arab League decision after Syria agreed to extend the observer's mission for another month. The official said the halt aims "to pressure the talks in order to call for external intervention in Syria's internal affairs," referring to the U.N. talks.

Elaraby's deputy, Ahmed Ben Heli, told reporters that the around 100 observers will remain in Damascus while their mission is "reevaluated." He suggested the observers could resume their work in the future...

Elaraby and the prime minister of Qatar were set to leave for New York on Sunday to seek U.N. support for the latest Arab plan to end Syria's crisis. The plans calls for a two-month transition to a unity government, with Assad giving his vice-president full powers to work with the proposed government.

Syria has rejected the proposal, saying it violates its sovereignty. Elaraby had previously been due to travel Saturday, but his trip was pushed back to Sunday with no explanation.

The U.N. Security Council began closed-door negotiations Friday on a new Arab-European draft resolution aimed at resolving the crisis, but Russia's envoy said he could not back the current language as it stands.

Any resolution faces strong opposition from China and Russia, and both nations have veto power. Russia's U.N. Ambassador Vitaly Churkin told reporters that the text introduced by new Arab Security Council member Morocco has "red lines" for Moscow, but he's willing to "engage" with the resolution's sponsors.

Churkin said those lines include any indication of sanctions, including an arms embargo. "We need to concentrate on establishing political dialogue," he said.