GENEVA (AP) – The U.N.’s top human rights official called Friday for the Sudanese government to carry out an impartial investigation into allegations its soldiers took part in the rape of women in Darfur last December.

At least 15 cases of rape and sexual assault at the hands of uniformed men were reported in the eastern Jebel Marra region of Darfur, according to a statement issued by the office of the U.N. High Commissioner for Human Rights, Louise Arbour.

“Victims were as young as 13 years old and at least two pregnant women were targeted in the violence,” the statement said.

Based on testimony collected by 30 U.N. human rights investigators working in Darfur, “it appears that rape during the December 2006 attacks was used as a weapon of war to cause humiliation and instill fear into the local population.”

The Darfur region of western Sudan has been the scene of a bloody four-year conflict between government-backed militias and rebel forces. More than 200,000 people have been killed and at least 2.5 million driven from their homes, according to U.N. estimates.

Sudan has consistently denied claims its forces have committed war crimes in the troubled region. It has refused to work with prosecutors at the International Criminal Court in The Hague who have named a junior minister and an alleged militia leader as war crimes suspects.

A report last month by a group of experts led by U.S. Nobel laureate Jody Williams said the government of Sudanese President Omar al-Bashir was responsible for orchestrating militia attacks on civilians, a charge it vehemently denied.

The statement from Ms. Arbour’s office Friday also called for an investigation into the alleged abduction of 19 men who went missing in southern Darfur in September. The investigators said armed men belonging to the Sudan Liberation Army faction of rebel leader Minni Minnawi arrested the men belonging to the Massalit tribe.

Three of the men were later released, the report said, but the whereabouts of the others remains unclear.

Government forces in January found eight bodies, identified by relatives as being those of some of the abducted men. The report says other members of the group may be among 25 bodies that were exhumed in October close to where the men were arrested.

The U.N. agency said it had received credible witness reports that the detainees had been tortured in the presence of SLA leaders.

Ms. Arbour’s office called on Minnawi, whose group signed the Darfur Peace Agreement last May and who is now chairman of the Transitional Darfur Regional Authority, to ensure the physical well-being of the detainees and allow U.N. human rights officials to meet them.

“If the captured persons are dead, there must be an independent, transparent, and timely inquiry to identify those responsible and hold them accountable for crimes that may have been committed,” she said.

On Monday, gunmen believed to belong to Minnawi’s faction killed two African peacekeepers and critically wounded a third in Geraida, according to the African Union.