Activists say Syrian warplanes have bombarded jihadi positions in the northern province of Raqqa as Muslim extremists close in on the last army base in the region.
The Tabqa air base is the last position held by Syrian government troops in Raqqa province - which is mostly under the control of the extremist Islamic State group.
The Britain-based Syrian Observatory for Human Rights reported intense clashes between troops and Islamic State fighters on the edge of the villages of Ajil and Khazna.
It said there were casualties on both sides.
The Raqqa Media Centre (RMC), an activist collective, said Islamic State group fighters captured four villages near Tabqa air base, including Ajil.
The Observatory and RMC also reported intense air raids for the second day on Raqqa's provincial capital.