Syrian forces have entered the southern town of Tafas near the city of Deraa in the Hauran Plain, according to residents.
They say at least eight tanks have moved into the town of about 30,000 people.
The residents say they heard gunfire and army and security forces broke into houses to arrest youths.
There are also reports saying troops have moved into the city of Homs north of Damascus on Sunday.
The BBC reports that residents of Homs contacted by telephone said that troops moved in overnight and started raiding homes, apparently looking for wanted people.
There's no word so far of casualties.
Troops enter Baniyas
Troops and tanks were reported to have swept into the Syrian city of Baniyas on Saturday, a centre of anti-government protests.
Activists say at least six people were killed, including four women who had staged a protest asking for the release of people recently arrested, the BBC reports.
The troops and tanks reportedly moved into Baniyas in the early hours of Saturday having circled the city since Wednesday.
The BBC said communications to the city and surrounding areas appear to have been cut, making the reports hard to verify.
'Thousands' in Friday demonstrations
Activists and witnesses said at least 26 protesters were killed by Syrian security forces when thousands demonstrated after Friday prayers in cities across the country, demanding an end to President Bashar al-Assad's rule.
The bloodiest confrontation on Friday was in the city of Homs where 15 protesters were killed, according to one activist.
The European Union has agreed to impose sanctions in response to Mr Assad's violent crackdown on protesters, which rights campaigners say has killed more than 580 people. It is to impose travel bans and asset freezes on at least 13 senior Syrian figures for their part in the violent crackdown.
The United States imposed sanctions of its own last week against some figures in the Syrian government.
On Saturday the US administration threatened to take new steps against President Bashar al-Assad's government if it does not stop killing and harassing its people.
A Western diplomat says 7000 people have been arrested since the demonstrations broke out in mid-March in Deraa.