Syria's state-run news agency and an opposition monitoring group say government troops have recaptured a town in Aleppo province from Islamic State militants.

The victory is key for Syria's military access to the provincial capital, Aleppo city.

SANA says the army took the town of Khanaser on Thursday, after three days of heavy battles with the extremist group.

The report says heavy fighting was ongoing to reopen the road to Aleppo city. IS seized Khanaser and surrounding hills on Tuesday, cutting the government's main land route to the city.

The Syrian Observatory for Human Rights, an opposition monitoring group, says the army and pro-government Shiite militias were backed by Russian airstrikes in the push on Khanaser.

The advance comes ahead of a cease-fire meant to start on midnight Friday.