The Sunni jihadist group Islamic State has beheaded 34 members of rival militia during a battle for the coastal Libyan city of Sirte, media reports said.

The IS militants on Friday stormed a hospital in the city and executed 22 wounded Sirte residents who were part of a local militia. The militants then mutilated their bodies before burning down the hospital building, according to Alwasat.

The brutal Islamist outfit also beheaded 12 others fighters and hung them at a public place as a warning to others, reported Agence France Presse.

A deadly confrontation between an Islamic State affiliate - State Organisation - and rival militia has claimed many lives in Serte's district no 3, reported Libyan news agency LANA. The state organisation has besieged Sirte's district No 3 since Wednesday.

An eyewitness said Sirte's main streets were almost deserted, most shops were shut, and there were shortages of food, medicine and fuel after full control of State Organization of the residential area (District 3) and the city as a whole, according LANA.

"A real war has been going on in Sirte since Tuesday. IS militants and armed residents from the city have been fighting continuously," a Sirte City Council member said, according to DW.

Libyan ambassador to France, Chibani Abuhamoud, said the bloody confrontation between ISIS militants and a local militia left between 150 and 200 dead.

"A real massacre is taking place, and we call on the international community to intervene," Abuhamoud told Agence France Presse.

Libyan Air Force on Sunday conducted airstrikes on positions of militants in the city.

"I received the confirmation that the Libyan Air Force warplanes conducted air strikes on Sunday morning. They took off from Misurata (city in north-western Libya) and hit the targets," a Libyan official told Sputnik.