Libyan forces are securing and de-mining areas newly captured from Isis in Sirte, combing the area around a convention complex that had been a symbol of the militant group's authority in the city.
Forces aligned with Libya's UN-backed government seized the Ouagadougou convention centre and several other key sites on Wednesday, advancing into areas that had been fought over for weeks.
Those forces, supported since 1 August by US air strikes, said in a statement that they had taken Isis's "most important bastions" in its former North African stronghold.
But they have yet to gain control of several neighbourhoods in central Sirte where an unknown number of militants are dug in. Eighteen government-aligned fighters were killed and 72 wounded, Rida Issa, a spokesman for the Sirte operation, said.
There has been house-to-house fighting in residential areas in recent weeks, with the brigade fighters struggling to gain ground against sniper fire, trip wires and landmines.
The fighters are led by brigades from the nearby Misrata, who repelled an Isis advance south of their city in early May before pushing eastwards to Sirte and besieging the militants in the centre of the Mediterranean city.
The capture of Sirte would be a major setback for Isis, ousting the jihadist group from the only city in Libya where it established total control.
It could also boost the fortunes of the UN-backed government, which has been struggling to impose its influence on a country riven by political and armed rivalries.
Brigades fighters found a house used as a laboratory for making explosive belts and seized a number of military vehicles used by Isis, some damaged and some in good condition, the spokesman, Issa said.
"Military engineering units are now working to clear the captured areas of mines," he added.
From an estimated fighting force of some 6,000 men, more than 350 brigade fighters have been killed and at least 1,500 since the campaign to recapture Sirte began.
On Wednesday, Mokhtar Fakron, an air force spokesman was killed with another pilot when their jet came down over Sirte.
US drones and fighter jets have so far carried out 29 strikes in Sirte, targeting Isis fighting positions, vehicles and armaments, according to statements by US Africa Command.
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