By Ahmed Elumami
TRIPOLI (Reuters) - Libyan forces engaged in renewed clashes with Islamic State militants in Sirte on Thursday, a day after capturing a convention complex that had been a symbol of the militant group's authority in the city.
Forces aligned with Libya's U.N.-backed government seized the Ouagadougou convention center and several other key sites on Wednesday, advancing into areas that had been fought over for weeks.
Those forces, supported since Aug. 1 by U.S. air strikes, said in a statement that they had taken Islamic State's "most important bastions" in its former North African stronghold.
But they have yet to gain control of several neighborhoods in central Sirte. On Thursday, fighters advancing on a hotel and guest houses near Sirte's port exchanged sporadic fire with militants, said Rida Issa, a spokesman for the Sirte operation.
The forces said they had "made incursions" into Areas 1 and 3, two of the districts still occupied by militants, and that they had "dealt with a number of snipers hidden in a corner of the Ouagadougou hall complex ... they were eliminated."
The gains come after weeks of house-to-house fighting in residential areas, with sniper fire, trip wires and landmines slowing the advance.
The fighters are led by brigades from nearby Misrata, who repelled an Islamic State advance south of their city in early May before pushing eastwards to Sirte and besieging the militants in the center of the Mediterranean city.
The capture of Sirte would be a major setback for Islamic State, ousting the jihadist group from the only city in Libya where it established total control.
It could also boost the fortunes of the U.N.-backed Government of National Accord (GNA), which has been struggling to impose its influence on a country riven by political and armed rivalries.
In an interview with Italian newspaper Corriere della Sera on Tuesday, before the latest advances, GNA Prime Minister Fayez Seraj said he believed the defeat of Islamic State in Sirte would "not take too much time. Probably not months, just a few weeks".
After Wednesday's advances, brigade fighters found a house used as a laboratory for making explosive belts and seized a number of military vehicles used by Islamic State, some damaged and some in good condition, said Issa, the spokesman.
"Military engineering units are now working to clear the captured areas of mines," he added.
U.S. Africa Command said it carried out seven strikes in Sirte on Wednesday, targeting trucks mounted with heavy artillery, fighting positions, a vehicle-borne improvised explosive device and two supply trucks. U.S. drones and fighter jets have carried out 36 strikes over Sirte since Aug. 1.
Eighteen GNA-aligned fighters were killed on Wednesday and 72 wounded, Issa said. Among the dead was Mokhtar Fakron, a senior air force commander who was killed with another pilot when their jet came down over Sirte.
From an estimated fighting force of some 6,000 men, more than 350 brigade fighters have been killed and at least 1,500 wounded since the campaign to recapture Sirte began.
(This story has been refiled to drop the extraneous word 'found' in paragraph 5)
(Additional reporting and writing by Aidan Lewis; Editing by Robin Pomeroy and James Dalgleish)