Nine Syrian judges and prosecutors also defected to the opposition. It was the latest setback for the regime which in recent weeks has seen a tough rebel challenge in its seat of power, Damascus, and has lost two airbases to opposition fighters.
In Lebanon, fighting between pro-and anti-Assad gunmen flared as bodies of three Lebanese who fought in Syria's civil war were brought back home for burial, the state-run National News Agency said.
Four people were killed and 12 were wounded in the gunfights, the agency said.
Syria civil war has often spilled into neighboring countries including Turkey, Lebanon and Israel, raising concerns of a wider war in the volatile region.
Lebanon, which Syria dominated for decades, is particularly vulnerable to getting sucked into the crisis. The two countries share a porous border and a complex web of political and sectarian ties.
Syria's opposition is dominated by members of the Sunni Muslim minority. Assad's regime is predominantly Alawite, an offshoot of Shiite Islam.
Tripoli has been the scene of frequent sectarian clashes between the Alawite and Sunni Muslim communities. Last week, the Lebanese army sent additional troops to Tripoli to try to prevent clashes that broke out over reports that 17 Lebanese men were killed after entering Syria to fight alongside the rebels.
In Syria, fighting between opposition fighters and regime troops was concentrated in northern Idlib province, in the Damascus suburbs and in Aleppo, Syria's largest city, according to the Britain-based opposition activist group Syrian Observatory for Human Rights. At least 21 people were killed in fighting Sunday, said the group, which relies on reports from activists on the ground.
The defecting judges posted a joint statement online urging others to join them and break ranks with Assad's regime. There have been a series of high-level defections over the past year, including Assad's former prime minister.
The Observatory said the latest defectors came from the northern city of Idlib.
Associated Press Jamal Halaby in Amman, Jordan contributed to this report.