The U.N. human rights office is calling for an investigation into alleged war crimes committed in Sudan's Southern Kordofan state.

The office said Monday it has received reports of indiscriminate killings, widespread looting, and massive civilian displacement in the state, where forces allied to what were then northern and southern Sudan clashed during June.

A 12-page report says beginning June 7 in the town of Kadugli, northern forces shelled civilian areas, executed pro-southern residents, and looted and destroyed civilian homes.

The fighting preceded South Sudan's split from the north in July, six years after a long civil war. The Khartoum government had ordered former southern fighters in the state to disarm or move south.

The U.N. report blames most of the abuses in Southern Kordofan on the north's army, police, and allied militia.

The U.N. high commissioner for human rights, Navi Pillay, says it is “essential” that an independent panel be allowed to investigate.

Sudanese President Omar al-Bashir is wanted by the International Criminal Court on charges of war crimes and genocide in Sudan's Darfur region.