"Commanders of front line units have counted at least corpses (of extremists) killed as they tried in vain to attack behind the lines" of the loyalists, said the media office of forces loyal to the Government of National Accord (GNA).
It said in a statement sent to AFP that the bodies of another 25 extremists were found in alleyways of the battleground coastal city.
The pro-GNA forces, who reported eight soldiers killed and 57 wounded Sunday, said vehicles, arms and ammunition were seized in the latest round of an assault launched on May 12 and executed in phases to recapture Sirte from ISIL.
A Dutch journalist covering the clashes in Sirte, Jeroen Oerlemans who worked for the Belgian weekly Knack, was shot dead Sunday.
Oerlemans became the second journalist killed in the fighting in Sirte after Abdelqader Fsouk, a Libyan who died in July.
On Saturday, GNA aircraft conducted six sorties in preparation for another advance on the extremists' last hideouts in the city's east.
The fighting has left more than 450 GNA fighters dead and 2,500 wounded. The ISIS death toll is not known.