The Syrian air force hit an Islamic State-controlled air base in Raqqa province on Tuesday, killing more than 140 militants, state media said, striking the jihadi group in its Syrian stronghold a week after it seized Palmyra from the government.

The city of Raqqa is seen as the de facto capital of the caliphate Islamic State has declared in Syria and Iraq. The group has made notable gains in both countries this month, capturing both Ramadi in Iraq and Palmyra in Syria.

It was not possible to independently verify the reported attack on the Tabqa air base, which Islamic State seized in August, killing scores of captive government soldiers.