Tripoli, June 11 : Dozens of mass graves have been found in the Libyan city of Tarhuna, some 90 km south of capital Tripoli, Interior Minister of the UN-backed government Fathi Bashagha said. "We discovered many terrible crimes committed by the militias that controlled the city of Tarhuna. Our services are now documenting those crimes," Bashagha said in a statement on Wednesday. Before the UN-backed government took control of it, Tarhuna was the main military operation centre for the east-based army, reports Xinhua news agency. "We found a container, inside which were prisoners who have been burned alive. We also found a number of mass graves, where according to our initial reports dozens of people were buried alive," the Minister said. "Those militias must be held accountable for their hideous crimes, and the politicians and military leaders who have provided these militias with cover must also be brought to justice." There was no comment on the development from the east-based army, which has been retreating in recent weeks in its military campaign against the troops of the UN-backed government. Also on Wednesday, the UN Mission in Libya said that warring sides in the country have begun to engage in a new round of ceasefire talks, after heavy fighting around the central city of Sirte. The east-based army has been fighting the UN-backed government troops for more than a year aiming to take control of Tripoli and topple the UN-backed government. The fighting has killed and injured hundreds of civilians and displaced more than 150,000 others. /IANS