More than 60,000 people have died in Syria's uprising and civil war, the United Nations said on Wednesday, dramatically raising the death toll in a struggle that shows no sign of ending.

In the latest violence, dozens were killed in a rebel-held Damascus suburb when a government airstrike turned a gas station into an inferno, incinerating drivers who had rushed there for a rare chance to fill their tanks, activists said.

"I counted at least 30 bodies. They were either burned or dismembered," said Abu Saeed, an activist who arrived in the area an hour after the raid in Muleiha, a suburb on the eastern edge of the capital.