Syria's allies in Russia called for urgent talks Thursday between Damascus and the opposition, saying an attack by Syrian renegade troops on a government building looks like the start of a civil war.

President Bashar Assad is facing severe international isolation stemming from his crackdown on an eighth-month-old uprising, which the UN estimates has killed 3,500 people. The Arab League suspended Damascus on Wednesday and threatened economic sanctions if the violence continues.

"This is all looking very much like a civil war," Russian Foreign Minister Sergei Lavrov told reporters in Moscow, referring to a pre-dawn attack on Wednesday by the Free Syrian Army, a group of army defectors determined to bring down the regime.

Wednesday's attack could not be independently confirmed, and the Free Syrian Army released no details about the fighting or possible casualties.

The army defectors reportedly fired machine guns and rockets at an Air Force Intelligence base just outside Damascus -- a brazen attack that sent a strong signal the popular uprising could descend into an armed conflict.

Russia calls for negotiations

Lavrov urged Syrian and opposition forces alike to cease violence and negotiate.

"Violence is not only coming from the authorities," he said. "More and more weapons are smuggled in from foreign states."

Earlier this week, Lavrov suggested Western countries were exacerbating problems in Syria.

"When these people hear tough statements from Washington and Brussels saying no dialogue should be held with (Assad) and he should resign, of course, this does not move to constructive talks," Lavrov was quoted as saying by the ITAR-Tass news agency.

Even as Assad was losing allies in quick succession, Russia and China kept up their long-standing ties with Damascus. In October they vetoed a UN Security Council resolution that threatened sanctions against Syria.

But on Thursday, Chinese Foreign Ministry spokesman Liu Weimin appeared to suggest Beijing might support a resolution in the future.

"It depends on whether these actions will help to resolve the tensions in Syria and facilitate the resolution of disputes through political dialogue," he said.

He called on both sides in the conflict to work together. The crisis appears to be spiraling out Assad's control, however, as attacks by army defectors increase and world leaders look at possibilities for a Syrian regime without him.

Syrians living in Jordan shout slogans against Syria's President Bashar Al-Assad during a demonstration in front of the Syrian embassy in Amman on Thursday. Majed Jaber/Reuters

Germany, Britain and France are pressing for a UN resolution that would strongly condemn Syria's human rights violations. The three European countries decided to move ahead with the General Assembly resolution after the Arab League confirmed its suspension.

"We hope it will show Assad just how isolated he is," Germany's UN Ambassador Peter Wittig said of the resolution.

World must 'hear screams' from Syria

Turkey's prime minister, Recep Tayyip Erdogan, said Thursday the world must urgently "hear screams" from Syria and do something to stop the bloodshed.

He said the uprising in Libya got far more worldwide attention because Libya has more oil.

"The lack of reaction to massacres in Syria was causing irreparable wounds in the conscience of humanity," he said..