7 loyalist troops killed fighting IS in Libya's Sirte
Fighting was fiercest around Sirte's conference center, which has become a command headquarters for IS at the heart of the city, a statement from forces loyal to the UN-backed Government of National Accord (GNA) said.
"The field hospital announced that seven martyrs perished and 49 were wounded in ongoing clashes between our forces and IS," it added.
Pro-GNA forces launched an operation in May to recapture Sirte, 450 kilometers (280 miles) east of Tripoli, after the extremists overran the city in June last year.
Its fall would be a major blow to IS, which has faced a series of setbacks in Syria and Iraq.
The two-month battle for Sirte has killed around 250 pro-government fighters and wounded more than 1,400, according to medical sources at the unity forces' command center.
The pro-GNA forces are mostly made up of militias from western Libya established during the 2011 revolt that overthrew dictator Moammar Gaddafi.
A militia set up to guard the country's main oil facilities has also been advancing on IS.
The GNA was the result of a UN-brokered power-sharing agreement struck in December, but it has yet to be endorsed by Libya's elected parliament based in the country's far east.