As in other towns, electricity and water were cut, at least temporarily.

Fighting was reported in Homs, Syria’s third largest city, which tanks entered Friday. Mr. Tarif said 14 people had been killed there; he could not confirm the casualties in Baniyas. Videos smuggled out of Homs, their authenticity undetermined, showed gunfire and crowds of people running for cover across a grassy lot. Mr. Tarif said the military also entered Tafas, in southern Syria.

Image Credit... The New York Times

“This is a campaign that’s going to more cities,” he said. “It’s escalating, and it’s very worrying because they’re also getting better at isolating these places.”

He said his group had documented 750 arrests, most of them in the Damascus suburbs, though he had no precise figures for Homs and Baniyas.

The uprising began in mid-March with protests in Dara’a, a town near Tafas and the border with Jordan. The protesters gathered after security forces arrested and mistreated high school students for scrawling antigovernment graffiti. The unrest soon spread, with successive Fridays in which thousands took to the streets in dozens of towns. The military’s presence in Tafas on Sunday suggests that the plight of Dara’a, part of a landscape knit tightly by extended clan loyalties, has roiled the region around it, a fertile but drought-stricken plateau famous for wheat and vineyards.

The military said it was withdrawing from Dara’a last week, and while armed columns were filmed departing, residents say the military remains in force. Townspeople were allowed to leave their homes Sunday from 8 a.m. to noon, activists said, and intermittent electricity and water were restored to some areas.

The Syrian government has sent signals to allies, in particular neighboring Turkey, that it is prepared to undertake some reform and begin a dialogue with opponents. But after a series of half-hearted concessions — sweeping in rhetoric but negligible in impact — the government repeatedly has met protesters with tear gas and live fire and sent its security forces to arrest thousands, by activists’ count, sometimes going door to door and randomly picking up any man older than 15.

The government has dismissed the estimates, saying it is engaged in a fight with militant Islamists, and American officials acknowledge that some protesters have been armed. Syrian television is suffused with images of soldiers’ burials. On Sunday, the Syrian news agency said that the authorities had seized sophisticated weapons and that the army was pursuing “armed terrorist groups” in Baniyas and elsewhere.