MORE than a dozen bodies have been unearthed from a mass grave near the northern Iraqi city of Tikrit, as a new UN report said Islamic State (IS) militants may have committed genocide, war crimes and crimes against humanity during their rampage across the country.

The discovery and the report’s findings – detailing mass killings, torture and rape – raised fears that more atrocities could be uncovered as Iraqi security forces and Shia militias claw back territory from the extremist group.

Iraqi authorities in Salahuddin province unearthed 13 bodies in the district of al-Boajeel, where forces are engaged in a large-scale offensive against the militants.

Video footage shows police digging up bodies and loading them onto trucks in plastic bags.

A government official and a senior military official said an investigation is under way to identify the dead. They said the site is not believed to be linked to the mass killing last summer of captured Iraqi soldiers from Camp Speicher, a nearby military base.

Iraqi troops backed by Shia militias are currently in a holding position on the edges of Tikrit as they wait for any remaining civilians to leave before pushing toward the centre of the city.

IS captured Tikrit and Iraq’s second largest city, Mosul, during its rapid advance across north and west in June. The extremists now rule a vast area straddling the Syria-Iraq border in which they have imposed a harsh version of Islamic law.

The UN report, published by the Human Rights Office, draws on the testimony of 100 people who survived attacks by the militant group in Iraq between June 2014 and last month.

“Clearly international war crimes and crimes against humanity and possibly genocide appear to have been committed during this conflict,” Hanny Megally, chief of the Middle East branch of the UN Human Rights Office said. The accounts detail killings, torture, rape and sexual slavery, forced religious conversions and the conscription of children.