Syrian troops besiege Islamic State held northern stronghold

Beirut: Syrian government forces are besieging the last Islamic State stronghold in the northern province of Aleppo, weeks after launching an offensive to free the entire province from militants.

The push on Deir Hafer comes as US aircraft ferried Syrian Kurdish fighters and allies behind IS lines to spearhead a major ground assault on the strategic IS-held town of Tabqa in Raqqa province, which borders Aleppo.

That airlift marked a deepening US involvement in Syria's conflict ahead of a looming battle for IS's de facto capital, the city of Raqqa.

The Syrian Central Military Media says Syrian troops launched the Deir Hafer siege late yesterday after capturing nearby areas.

The opposition's Britain-based Syrian Observatory for Human Rights says Syrian troops have now cut the road linking Deir Hafer with Raqqa province.