Libya pro-government forces repelled a counterattack by the Islamic State group as they pressed their offensive to retake the jihadist coastal bastion of Sirte on Friday, a military statement said.

Forces backing Libya's unity government early Friday "repelled a new counter-offensive from Daesh... in very violent clashes," the statement said, using an Arabic acronym for IS.

At least 10 jihadists were killed in the fighting, it said. In a later statement it said four members of the GNA forces were killed in today's clashes and 24 others were wounded.

Since May 12, pro-government forces from the west, Libyan naval forces and eastern militias have pushed the jihadists back into a residential zone of just five square kilometres (two square miles) inside the city. 

But their early advances slowed when they entered Sirte on June 9 and reached built-up central and northern parts of the city. IS has hit back with suicide car bombs and sniper fire.

The jihadists overran the city some 450 kilometres (270 miles) east of the capital in June last year.

Pro-government forces retaking the city would be a major blow to IS, which has faced a series of setbacks in Syria and Iraq.

Nearly 200 anti-IS fighters have been killed and over 600 injured since the start of the offensive, according to medical sources.

Pro-government forces, commanded out of Misrata -- 190 kilometres to the northwest -- are mostly made up of western militias that were born during the 2011 revolt that overthrew dictator Moamer Kadhafi. 

A militia set up to guard the country's main oil facilities has also been advancing on IS from the east.

Source: AFP