Bomb blasts killed 14 prisoners travelling in a security vehicle in northwest Syria on Saturday, the state news agency said, and troops fought rebels elsewhere as the Arab League weighed whether to keep monitors in place.
Syria's SANA agency said a terrorist group had set off two explosions that also wounded 26 prisoners, as well as six police guards. It said the assailants had also attacked ambulances sent to the scene, on the road between the towns of Idlib and Ariha.
The British-based Syrian Observatory for Human Rights, which tracks the 10-month-old revolt against President Bashar al-Assad, had earlier reported the attack in northwestern Idlib province.
It said army troops were clashing with soldiers who have deserted and joined an anti-Assad insurgency in the Jebel al-Zawiya region of Idlib, which is near the Turkish border.
Al Jazeera television said army troops and deserters were also battling in the northwestern city of Jisr al-Shughour.
The Arab League looks set to extend its monitoring mission in Syria, given the lack of any Arab or world consensus on how to halt bloodshed there, an Arab diplomatic source said.
Sudanese General Mohammed al-Dabi, head of the 165-strong monitoring team, was due in Cairo on Saturday to submit his report for a League committee on Syria to consider the next day.
Hundreds of people were killed during the month-long observer mission, despatched to assess Syria's implementation of an Arab peace plan originally agreed in early November.
Syria, keen to avoid tougher action by the Arab League or by the United Nations, has tried to show it is complying with the plan, which demanded a halt to killings, a military pullout from the streets, the release of detainees, access for the monitors and the media, and a political dialogue with opposition groups.
Yes, there is not complete satisfaction with Syria's cooperation with the monitoring mission, the Arab source said. But in the absence of any international plan to deal with Syria, the best option is for the monitors to stay.
Critics say the Arab monitors have only given Assad diplomatic cover to pursue a bloody crackdown on his opponents.
This month the Syrian authorities have freed hundreds of detainees, announced an amnesty, struck a ceasefire deal with armed rebels in one town, allowed the Arab observers into some trouble spots and admitted a gaggle of foreign journalists.
Assad also promised political reforms, while vowing iron-fist treatment of the terrorists trying to topple him.
Burhan Ghalioun, head of the opposition Syrian National Council which has called for international action to protect civilians in Syria, was also in the Egyptian capital for meetings with opposition colleagues and Arab League officials.
Western powers remain sharply critical of what French President Nicolas Sarkozy denounced on Friday as Assad's ferocious repression of his people, but have failed to overcome Chinese and Russian opposition to any U.N. Security Council resolution condemning Syria or imposing sanctions.
The United States and the European Union have toughened their own punitive measures, but have no desire to mount a Libya-style military intervention to help Assad's opponents, who include armed insurgents as well as peaceful protesters.
Washington warned on Friday that it may soon close its embassy in Syria due to worsening security conditions and said it believed Assad no longer had full control of the country.
U.S. concern about the safety of its mission in Damascus, which was attacked by a pro-Assad crowd in July, intensified after three deadly blasts in the Syrian capital in recent weeks, blamed by Syrian authorities on al-Qaeda suicide bombers.
Closing the embassy would not amount to cutting diplomatic ties, but would reduce direct U.S. contacts with Damascus.
A White House spokesman said Assad's fall was inevitable and demanded he halt violence against protesters in which the United Nations says more than 5,000 people have died since March. Syria says 2,000 security personnel have been killed.
At least six people were killed on Friday and the bodies of six others were returned to their families, activists said.
(Additional reporting by Ayman Samir in Cairo and Andrew Quinn in Washington; Editing by Giles Elgood)