Tripoli - The Islamic State of Iraq and the Levant (ISIS) has brutally quelled a rebellion in the Libyan city of Sirte by citizens who took up arms to try to push back the armed group, residents have said.Witnesses said the group was now calling on residents to pledge allegiance over loudspeakers from its main mosque and desecrating bodies of their adversaries.Sources in the city told Al Jazeera on Monday that clashes broke out five days earlier between ISIS and armed residents in the city's Number Three neighbourhood, before ISIS besieged it and began shelling it with heavy weaponry.By Monday, the neighbourhood was under the full control of ISIS, the sources said.Cleric Khalid Awad said that ISIS had killed some of their prisoners and hung the bodies from bridges, roundabouts and highways across the city, the AFP news agency reported. There were also reports that the group had beheaded 12 people and crucified them. Libya's National News agency said the beheadings took place in the Number Three neighbourhood.The Reuters news agency quoted witnesses as saying that ISIL had also hung the bodies of four fighters over bridges for public display.ChaosISIS began to make advances in Sirte earlier this year, taking advantage of the chaos plaguing Libya since 2011. There are now two rival governments in the country, a UN-recognised government in Tobruk, and a legally-installed government in Tripoli. These are also combined with an assortment of tribesmen and armed groups, all battling for control of cities and regions after leader Muammar Gaddafi was ousted and killed by rebel fighters four years ago.Libya's UN-recognised government has appealed to neighbouring Arab states to conduct air strikes against ISIS in Sirte.A statement made by government officials 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 co-ordination with our concerned bodies."The government also condemned the reluctance of the international community to take action against ISIS.The two rival governments have conducted air strikes against ISIS in Sirte in recent days, but their capabilities are very limited, relying on outdated warplanes and helicopters from the Gaddafi era, and a lack of precision guns.In response to Libya's call to arms, the Arab League said it would hold a meeting on Tuesday to discuss the request.'Barbaric' actsOn Sunday, the governments of the US, France, Germany, Italy, Spain and Britain issued a joint statement condemning the "barbaric" acts carried out by ISIS in Libya.The statement, released by the US state department, said that the nations "are deeply concerned about reports that these fighters have shelled densely populated parts of the city and committed indiscriminate acts of violence to terrorise the Libyan population".The governments called for all parties in Libya "to join efforts to combat the threat posed by transnational terrorist groups exploiting Libya for their own agenda".The statement added that: "There is no military solution to the political conflict in Libya."