BEIRUT, Lebanon — At least 30 people, and possibly dozens more, were killed in Syria on Thursday in northern Raqqa Province when government warplanes bombed a gas station crowded with cars and people, according to a witness at the scene and activist groups.

The witness said the gas station was on the outskirts of Ayn Issa, a town near a border post with Turkey that Syrian opposition fighters had stormed two days ago.

The Syrian Observatory for Human Rights, a group based in Britain with a network of contacts in Syria, said 110 people were killed or wounded.

If verified, the bombing would be one of the worst casualty tolls from the Syrian military’s use of aircraft in its effort to crush the armed insurgency. Stretched thin by a persistent, far-flung rebellion, and facing greater challenges from improvised bombs on Syria’s roads, the military has increasingly relied on warplanes and helicopters to extend its reach.