CNN reported the Syrian Observatory for Human Rights said the forces clashed with the gunmen, believed to be dissidents, amid gunfire and explosions in the city of Binnish in Idlib province.
"Syrian military forces supported by tanks and armored personnel carriers stormed the city early this morning," the group said. "Heavy machine guns and shelling have been heard around the city."
Some houses were damaged and casualties were reported, the group said.
Oudai al Sayed, an opposition activist, said seven people had been killed, including a 2-year-old boy.
The human rights group said military forces also stormed the village of Taoum east of Binnish.
In Homs province in western Syria, the group said, forces raided al-Qusor and arrested 19 people.
Al Sayed said he escaped Binnish through olive groves and saw 30 tanks and an armored personnel carrier entering the town, CNN reported.
A few months ago, military defectors had taken refuge in Binnish and some of them are fighting Syrian troops, he said.
For seven months, protesters in Syria have been demanding the ouster of President Bashar Assad's regime and democratic elections. The Syrian Observatory estimates more than 3,100 people have died, 2,400 of them civilians, since the uprising began.