Isis militants are reported to have beheaded 12 people and crucified their bodies during the fight for the Libyan city of Sirte.
The Libyan government said that there was a "massacre" going on in the city, with the local Isis affiliate pushing to expand the areas it controls.
The majority of Sirte fell into Isis's hands at the end of May, but a fierce battle for the eastern district known as "neighbourhood three" has been raging with local gunmen since Tuesday.
According to the Associated Press, Isis shelled the area, killed a senior cleric and hung the bodies of other prisoners over bridges.
Some 22 Sirte residents who joined the local militia were murdered by Isis while they lay wounded in hospital, the national LANA news agency reported. It said the jihadists also set the hospital itself on fire.
Libya Dawn fighters fire an artillery cannon at IS militants near Sirte March 19, 2015.
In a statement issued late on Saturday, the government said it could no longer fight the Isis advance alone and called for support from the international community.
It said: "The Libyan government, unable to ward off these terrorist groups because of the arms embargo, and out of its historic responsibility toward its people, calls on brotherly Arab countries ... to launch airstrikes against specific targets of (Isis) locations in Sirte in coordination with our concerned bodies." Timeline: The emergence of Isis
Speaking to the AFP News Agency, Libya's ambassador to France, Chibani Abu Hamoud, said up to 200 people had died in the battle for "neighbourhood three" so far.
"A real massacre is taking place, and we call on the international community to intervene," he said.
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