The pro-GNA forces, backed by aerial support of international forces, recaptured nearly all of what had been the militants’ main stronghold in North Africa, Middle East Eye reported.

The city's fall would be a huge setback to ISIS efforts to expand its self-proclaimed "caliphate" beyond Syria and Iraq where they have also suffered losses.

"The fighting has begun. We are attacking the last ISIS positions in district three" where the militants are cornered, a GNA fighter said to reporters.

By most estimates, ISIS had 2,000-5,000 militants before May in Sirte. Some are thought to have escaped near the start of the campaign and hundreds have been killed, though no figures are available.

Fewer than 200 ISIL militants remain in Sirte, Pentagon spokesman Captain Jeff Davis said on Thursday, and they are essentially surrounded by GNA forces and the sea.

The GNA forces media center confirmed on Facebook that the new push had begun to retake Sirte, located 450km East of the capital Tripoli

"Our forces are advancing inside the areas where ISIL is, in district three, and so far have taken control of" two banks and a hotel, the media center said.

It also said they had thwarted an attempted suicide bombing.

Seven members of the GNA forces were killed and 30 wounded in clashes with ISIS on Saturday, it added.

The forces loyal to the UN-backed GNA had said last weekend they were preparing to "liberate" the entire city after seizing several ISIS positions, including its headquarters.

On Wednesday, GNA head Fayez al-Sarraj visited Sirte for the first time since loyalist forces launched their offensive more than three months ago to drive the militants from the city, FNA reported.

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