Islamic State fighters fleeing the Libyan city of Sirte in the face of advancing Libyan government forces are shaving their beards to disguise themselves, military officials in the North African country have claimed.

Ahmed Hadiya, head of the media centre of the anti-IS operation room, on Thursday (9 June) told the Associated Press that some IS fighters were shaving off their beards and long hair in order to flee the coastal Libyan city under cover.

Reuters reported that armed brigades from Misrata, aligned with Libya's Government of National Accord, had made a rapid advance into Sirte from the west.

Military officials from Misrata, which emerged as one of the major military players in post-Gaddafi Libya, have predicted they will take back control of the city within 48 hours.

"We think that Sirte will be liberated within days not weeks," Gasri said. "The Daesh snipers are a concern to us because they shoot from long distances and that has hindered us in the battle inside the city," he added.

In an advance during which dozens of pro-government fighters have have been killed and hundreds wounded in the past month of fighting, the Misratan forces have seized control of a vital air base, several military camps and a central round about where IS militants had hung the bodies of executed enemies for intimidation purposes.

To the east, the Petroleum Facilites Guards, armed brigades under the control of Ibrahim Jadhran, have cleared vast swathes of the coastal road previously held by the Islamic State.

The offshoot of IS in Libya took complete control of Sirte when, at the end of May, the group captured the city's civilian airport, pushing out forces loyal to Libya's Tripoli-based government. IS has exploited a political vacuum in Libya over the past year, using a stalemate between the country's two rival governments to exert its control. A number of Islamist militias, remnants of Libya's 2011 liberation war, have allied themselves with the group.