Syrian activists say the Syrian army has carried out a wave of airstrikes in the northern city of Raqqa, the self-declared capital of the Islamic State group.

Two Syria-based groups as well as the Britain-based Syrian Observatory for Human Rights say warplanes carried out at least 12 airstrikes across the city Thursday. They reported casualties but had no specific figures.

The airstrikes occurred as the U.N. envoy to Syria, Staffan de Mistura, was in Damascus. De Mistura met with Foreign Minister Walid al-Moallem, who told him that fighting terrorism was the Syrian government's priority.

Syrian President Bashar Assad said in an interview with Russian media aired Wednesday that there can be no political solution to the Syrian civil war before terrorism is defeated.