BEIRUT, Lebanon - Violence across Syria killed at least 25 people Wednesday, including eight soldiers who were gunned down by army defectors in a retaliatory ambush after government troops destroyed a civilian car, activists said.

It was the second day in a row in which an attack by President Bashar al-Assad's forces on civilians appears to have brought a quick and deadly act of revenge by anti-regime fighters. The ambush was the latest sign the once-peaceful protest movement is growing into an insurgency.

The brazen midday attack came hours after troops fired on a civilian car traveling through the village of Khattab in the countryside of the central province of Hama, killing all five passengers inside.

The vehicle "exploded in a ball of fire," said Rami Abdul-Rahman, director of the British-based Syrian Observatory for Human Rights, which relies on a network of activists on the ground inside Syria.

Hours later, he said, gunmen ambushed a convoy of four military jeeps passing through the nearby village of al-Asharna on the northern outskirts of the city of Hama, spraying it with bullets. The gunmen are believed to be military defectors seeking revenge for the dawn attack targeting the car, he said.

There was no immediate claim of responsibility for the ambush, but the Free Syrian Army, a Turkish-based defector group, has in the past claimed similar attacks across the country.

Abdul-Rahman and other activists who confirmed the initial car attack did not say why soldiers targeted the vehicle, but security forces frequently hunt for suspects in the restive area.

"The area is a stronghold of dissent where anti-regime protests are routinely held and where there are a number of [army] defectors," he said.

The Local Coordination Committees group said the car was destroyed by a shell fired by the army. A third activist in Syria who spoke on condition of anonymity for fear of reprisal said the car was struck by bullets. The differing accounts could not be immediately reconciled.

Activists said 17 other people were believed killed by security forces in Homs, Idlib, Daraa, and elsewhere.

The observatory also reported heavy gunfire in Hirak village in the southern province of Daraa, as troops backed by tanks and armored personnel carriers hunted for activists. Three military defectors were wounded in clashes with Syrian security forces in the area, it said.

The United Nations says that more than 5,000 people have been killed since the revolt erupted in March.