Activists and Syria's state media are reporting that dozens of Islamic extremists have been killed in fighting around a northern military base.

Syria's state news agency SANA quoted an unnamed military official as saying that "large numbers of terrorists were wiped out" on Thursday near the Tabqa air base in the northern province of Raqqa.

The Britain-based Syrian Observatory for Human Rights says the death toll among fighters from the Islamic State group is at least 11 and possibly as many as "tens."

Beirut-based Al-Mayadeen TV said more than 150 members of the Islamic State were killed in an ambush near the air base. The base is the last army position in Raqqa province that is still under government control.