Saudi Arabia has pulled out of the Arab League monitoring mission in Syria, criticising Damascus for failing to act to stop violence against protesters.Foreign Minister Prince Saud al-Faisal called on the international community to put more pressure on the regime.
He was speaking at an Arab League meeting in Cairo, which is expected to extend the Syria mission for a month.
Critics have said the 165-strong mission has done nothing to stop a 10-month crackdown on protesters.
Activists say almost 1,000 people have been killed since the monitoring mission began.
The opposition Syrian National Council has formally asked the league to refer the crisis to the UN Security Council.
The league's foreign ministers are meeting in Cairo to discuss the conclusions of Syria mission chief Gen Mohammed al-Dabi.
General Dabi is believed to favour extending the mission and boosting the number of observers.
The BBC's Jon Leyne in Cairo says it is likely that the mission will be extended, but the Saudis might just have inflicted a fatal wound.
Prince Saud al-Faisal told the meeting that Riyadh was pulling out because the Syrian government had not followed an Arab peace plan it agreed to before the monitors were sent.
"We are calling on the international community to bear its responsibility, and that includes our brothers in Islamic states and our friends in Russia, China, Europe and the United States," he said.
Meanwhile, Syrian rebels said that army deserters had briefly taken control of much of the Damascus suburb of Douma on Saturday night after fierce fighting with the security services.
The opposition Syrian Observatory for Human Rights said the fighting broke out after security services shot dead four civilians at a funeral service.
The rebels later decided to withdraw for fear of reprisal raids from the government forces, the group said.
There has been no independent confirmation of any fighting in the area.
In a separate development, at least 14 people died after a van carrying prisoners was blown up on a road in north-west Syria on Saturday, reports say.
The official Sana news agency said the police van was attacked by an "armed group" on the Idlib-Ariha highway.
Opposition groups confirmed the attack but did not say who carried it out.
Activists said armed rebels then stormed the state hospital and found another 60 bodies in the mortuary, some of them showing signs of torture.
Rights activists also said 30 unidentified corpses had been discovered at the National Hospital in Idlib.
The UN says that more than 5,000 have died since protests against President Bashar al-Assad erupted last March.
The government in Damascus says that some 2,000 members of the security forces have also been killed combating "armed gangs and terrorists".