Armed Syrian rebels captured dozens of members of the security forces by seizing two military checkpoints in the northern province of Idlib on Monday, the opposition Syrian Observatory for Human Rights said.
It said the army deserters also clashed with security forces at a third checkpoint, killing and wounding an unspecified number of troops loyal to President Bashar al-Assad.
Rami Abdelrahman, director of the British-based Observatory, said Monday's operation took place in the Jabal al-Zawiyah region of Idlib. It was not immediately clear how many people had been killed or captured by the rebels, he said.
The Syrian government bars most international journalists from operating in the country, making it difficult to verify accounts of incidents.
The reported attack came three days after the anti-government Free Syrian Army said it had ordered its fighters to stop offensive operations pending a meeting with Arab League delegates monitoring Assad's compliance with a peace plan.
Monitors from the Arab League are checking Syria's compliance with an Arab peace plan that calls for Assad to withdraw troops and tanks from the streets, release detainees and talk to the opposition.
The United Nations says more than 5,000 people have been killed in the crackdown on protests which broke out against Assad in March. Syrian authorities say armed groups have killed 2,000 security forces personnel during the 10-month uprising.
Colonel Riad al-Asaad, commander of the rebel Free Syrian Army, said on Friday he had ordered fighters to halt all attacks when the Arab monitors first arrived in Syria 10 days ago.
But a video shot by rebel fighters last week showed the ambush of a convoy of army buses in which activists said four soldiers were killed.
(Reporting by Dominic Evans; Editing by Peter Graff)