Troops opened fired on a car traveling through central Syria early on Wednesday, setting it on fire and killing all five passengers inside, activists said.
The five were passing near the village of Khattab in the countryside of the central Hama province at dawn on Wednesday when their vehicle came under attack from Syrian soldiers, the Local Coordination Committees network and the British-based Syrian Observatory for Human Rights said.
The car "exploded in a ball of fire," said Rami Abdul-Rahman, director of the Observatory, which relies on a network of activists on the ground inside the country.
He did not say why the car was targeted, but security forces frequently hunt for suspected anti-government activists 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 LCC said the car was destroyed by a shell fired by the army. A third activist based in Syria who spoke on condition of anonymity for fear of reprisal said the car was struck by a hail of bullets.
The differing accounts could not be immediately reconciled.
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 anti-regime military defectors were wounded in clashes with Syrian security forces in the area, it said.
The new shootings follow a spike in violence which left 38 dead on Tuesday, mostly in a restive northwestern province where Syrian security forces faced off against armed defectors.
The fighting in Idbil province included an ambush by army defectors, who killed seven government troops in an attack on a security convoy in northern Syria.
It provides fresh evidence that the Syrian uprising is growing into a virtual insurgency, complicating an uprising against President Bashar Assad that began nine months ago as largely peaceful.
The UN says more than 5,000 people have been killed since the revolt erupted in March.
Separately, a pro-government Syrian newspaper reported on Wednesday that Syria's ambassador to the United States, Imad Mustafa, has been named envoy to China.
Al-Watan newspaper said Assad has issued a decree appointing Mustafa, who was recalled in October in response to the US administration's withdrawal of US ambassador Robert Ford from Damascus over security concerns. Ford returned to Syria last week.
There was no official confirmation from Syrian authorities of the newspaper report.
China, along with Russia two veto-wielding countries on the UN Security Council, have been supportive of Damascus. Last month it vetoed a Western-backed UN Security Council resolution condemning the bloodshed in Syria.