Isis Libya
The offshoot of IS in Libya parades through the Sirte SITE Intel

At least 37 people have been killed in clashes between Islamic State (Isis) and Islamist residents in the Libyan town of Sirte as locals challenge the militant group in its last stronghold in the country.

Libya's Prime Minister Abdullah Al-Thinni has condemned the violence in the strongest terms, referring to the bloodshed as genocide. "The Libyan government expresses its serious concern following events which are unfolding in the city of Sirte," he said in a statement. "It expresses deep regret and ardent condemnation of horrendous crimes of genocide against the city and its residents at the hands of the group Isis."

Reports in Libyan local media have characterised the violence as a vicious crackdown on dissent by IS, which has held the balance of power in Sirte since May.

Mohamed Eljarh, Nonresident Fellow for the Atlantic Council told IBTimes UK while reports on the ground were difficult to confirm that executions of members of the the Farjan tribe which had led the fightback against Islamic State in Sirte had been announced by the group's leader Hassan Karami for after Friday prayers.

"They are executing people publicly right now. Apparently there is an execution going on after Friday prayers of tens of people from the Ferjan tribe," Eljarh said.

"Today as al Karami was giving a sermon at one of the main mosques in Sirte he said there are people in pick up trucks outside from the Ferjani tribe and these people will be executed."

Libyan news website Bawabat Al-Wasat reported 22 people were killed when IS set fire to a hospital in Sirte treating wounded opposition fighters. It also claimed numerous kidnappings of residents had taken place in the past 24 hours. Meanwhile, Reuters reported that 37 people were killed in clashes over the past two days, quoting Sirte residents.

But Thinni called on the international community not to sit idly by in the face of the clashes and to supply Libya's internationally recognised government, which he heads in Tobruk, with arms to combat IS. Libya is subject to an ongoing international arms embargo.

Islamic State fighters raise their black flag over Sirte where they drove out Tripoli government forces in May YouTube

Salafists fighting along tribal lines attempted to wrest control of one neighbourhood, District No. 3 in Sirte in reaction to the killing of a prominent local preacher. The group seemed to take its lead from residents in Derna who successfully ejected IS alongside local Al-Qaeda-linked militias, after it had taken up residence in the town for almost a year.

Two foreign IS commanders in Sirte were killed in the clashes on 13 August, one from Egypt and another from Saudi Arabia, according to local media. The offshoot of IS in Libya took complete control of the central Libyan city of Sirte when, at the end of May, the group captured the city's civilian airport, pushing out forces loyal to Libya's Tripoli-based government. IS in Libya's influence around Sirte extends some 150km to the east, along the coastal road to the town of Nawfliyah.

At the beginning of March, 166 Battalion loyal to Tripoli began a campaign in Sirte, the hometown of Libya's former ruler Muammar Gaddafi, to rid it of the IS forces. However, despite some initial gains, the move proved unsuccessful.

IS has exploited a political vacuum in Libya over the past year, using a stalemate between the country's two rival governments to exert its control. A number of Islamist militias, remnants of Libya's 2011 liberation war, have allied themselves with the group.