Syrian government troops advanced overnight against the Islamic State group in the country's north and centre, drawing closer to the key battleground of Deir Ezzor, a monitor said.

The Syrian Observatory for Human Rights, a Britain-based monitor, said the army had made "significant progress" south of Raqa city.

"There is now just four kilometres between regime forces and the town of Madan, which is the last town controlled by Islamic State in the Raqa countryside," the Observatory said.

Madan lies next to the border between Raqa province and Deir Ezzor, an eastern province that is mostly held by the Islamic group.

Jihadists have besieged government forces and civilians inside the provincial capital Deir Ezzor city since 2015.

Syrian loyalist troops are battling Islamic State in the south of Raqa province separately from an offensive by the US-backed Syrian Democratic Forces, a militia that is fighting the jihadists inside Raqa city.

The regime is also fighting Islamic State in central Homs province, where overnight they captured the last jihadist-held town in the area, the Observatory said.

The capture of Al-Sukhna opens the route for government troops to advance towards Deir Ezzor on a second axis.

There was no official confirmation of Sukhna's capture from Syria's government.

State news agency SANA said the army had surrounded the town from three sides.

Since May, Syria's army has been conducting a broad military campaign with Russian support to recapture the vast Badia desert region that separates the capital Damascus from Deir Ezzor.

The Observatory said at least 64 Islamic State fighters were killed in clashes with the regime and air strikes across the Badia region on Saturday.

Among the dead were 30 killed in the fight for Al-Sukhna, the monitor said.

Already defeated in its Iraqi bastion of Mosul, Islamic State is facing multiple assaults in Syria.

The SDF now control more than half of Raqa city, a key Islamic State stronghold.

source: AFP