Pro-government forces pound Islamic State in Sirte

Militant positions were pounced by troops from the UN-backed Government of National Accord (GNA) as part of a major campaign to regain control of the hometown of former leader, Muammar Gaddafi.

"The countdown has begun," the GNA forces said on Twitter.

The loss of Sirte, is expected to be a major blow to the militants at a time when they are under increasing pressure in Syria and Iraq where they have lost swathes of ground in recent months.

The announcement follows the GNA’s announcement on Thursday which declared its forces had pushed into the centre of Sirte and expected it to fall within days.

"The operation will not last much longer. I think we'll be able to announce the liberation of Sirte in two or three days," said Mohamad Ghassri.

The United States welcomed the progress with several senior figures commenting on the “rapid advances”.

A US Defence Department spokesman confirmed GNA forces were "making progress".

"We certainly are encouraged by the progress we see those government forces making," Pentagon press secretary Peter Cook said.

But analysts maintain the defeat of IS in Sirte would not be the end of IS in Libya.

"If ISIS (IS) is defeated in Sirte, we expect an increase in attacks against oil installations to the south and also in the cities of Misrata and Tripoli," said Mohamed Eljarh of the Rafik Hariri Centre for the Middle East.

IS has fed on the political and military divisions that have plagued Libya since the 2011 uprising.

Foreign intelligence services estimate IS has 5,000 fighters in Libya but its strength inside Sirte and the number of civilians living in the city are currently unavailable.