MISRATA, Libya: Libyan pro-government forces are facing "fierce resistance" from ISIS holdouts in Sirte and it could take several days to gain full control of the city, a spokesman said Sunday.

Forces loyal to Libya's Government of National Accord (GNA) launched a new attack on Saturday against ISIS in Sirte, the coastal city seized by the extremists last year.

Backed by weeks of U.S. airstrikes, pro-GNA fighters have recaptured nearly all of what had been the extremists' main stronghold in North Africa.

ISIS fighters are now cornered in a last district of the city but Reda Issa, a spokesman for loyalist forces, said it was proving difficult to dislodge them.

"ISIS is putting up fierce resistance in their last neighborhoods," Issa told AFP. "They are trying to make the battle last longer although they know it will be over soon."

At least 10 pro-GNA fighters were killed and 60 wounded in Saturday's offensive, with most of the deaths caused by car bombs and suicide attacks, Issa said.

Fighting had eased on Sunday, he said, as pro-government forces sought ways "to minimize the casualties caused by ISIS suicide attacks the next time there will be an offensive."

"We hope to liberate Sirte before Eid," Issa said, referring to the Eid al-Adha Muslim holiday, which is due around September 12.

The forces loyal to the UN-backed GNA had said they were preparing to "liberate" the entire city after seizing several ISIS positions, including its headquarters, last month.

The city's fall would be a huge setback to ISIS's efforts to expand its self-proclaimed "caliphate" beyond Syria and Iraq where the extremists have also suffered losses.

The capture of Sirte by ISIS sparked fears the extremists would use the city as a springboard for attacks on Europe.