At least 34 Libyan fighters have been killed and more than 180 wounded as they closed in on the last Islamic State militant holdouts in the coastal city of Sirte, according to field hospitals.
Forces aligned with Libya's UN-backed government, supported since August by US air strikes, have pushed militants back into a small residential area in central Sirte in a three-month-old campaign.
Heavy fighting resumed on Sunday after a one-week lull.
The Libyan brigades, mostly from the city of Misrata, say they are close to victory in Sirte, but they have struggled to defend themselves against suicide bombings, sniper fire and landmines.
On Sunday several brigades stationed close to Sirte's seafront advanced several hundred metres eastwards through Sirte's neighbourhood, while other fighters overran Islamic State positions in street-to-street fighting to the south.
Fighters used tanks, rocket-propelled grenades and anti-aircraft guns to try to blast through Islamic State sniper positions.
The Misrata-led brigades said there had been five attempted car bombings on Sunday in a "desperate attempt to disrupt the advance", though at least one of the bombs had been destroyed before it could reach its target.
The front lines in Sirte were quieter earlier this week as government-led forces said they were giving time to the wives and children of Islamic State fighters to leave the battle zone.
Almost all the city's estimated 80,000 residents left after Islamic State took full control of the city last year, turning it into its regional stronghold and expanding its presence along about 250 km of coastline.
The United States has carried out dozens of air strikes against Islamic State positions and vehicles in Sirte.
Libyan commanders say some Islamic State militants probably escaped around the start of the campaign to recapture Sirte in May, and their forces have been trying to secure the desert to the south and west of Sirte.
