Assad has unleashed military and security forces on restive towns across the country to crush the unrest, but the uprising has been building steadily. Friday saw the largest protests yet with hundreds of thousands turning out nationwide to challenge the president's rule. About 30 people were killed on Friday and Saturday authorities rounded up more than 500.

On Sunday, residents in the eastern town of Al-Boukamal said about 150 soldiers arrived in helicopters, but there were no immediate reports of violence. The pro-government Al-Watan newspaper reported Sunday that a military operation in the town was imminent.

Activists reported that dozens of soldiers defected and joined protesters in Al-Boukamal late Saturday. The crowds chanted "the people and the army are one!" — echoing the rallying cries heard during Egypt's revolution.

The defections were reported by Syria-based human rights activist Mustafa Osso and Omar Idilbi, a spokesman for the Local Coordination Committees, which help organize and track the protests. Both cited witnesses on the ground to back up the defection reports.

A video posted on YouTube, purportedly from Al-Boukamal, showed scores of people marching and standing on two army tanks and one armored personnel carrier. No soldiers appeared in the video but the residents were chanting "the people and the army, one hand!"

Syrian troops also stormed a town near the Lebanese border on Sunday. The Local Coordinating Committees said some 2,000 military and security forces stormed into Zabadani, 40 km northwest of Damascus, after cutting the town's telephone services, Internet connections and electricity.

Activists say the government's crackdown has killed some 1,600 people since March, most of them unarmed protesters. But the regime disputes the toll and blames a foreign conspiracy for the unrest, saying religious extremists — not true reform-seekers — are behind it.

Also Sunday, authorities detained leading opposition figure Ali Abdullah after a raid on his home in the Damascus suburb of Qatana, his son Mohammad said. Abdullah, 61, had spent four years in jail but was released May 30 when Assad issued pardons to pacify the protesters.