The U.N. on Monday accused the Ugandan-based Lord's Resistance Army of killing, mutilating and raping villagers in Sudan and Congo in what may have been crimes against humanity.

The rebels killed at least 1,200 people and abducted 1,400, including children and women, in northeastern Congo from September 2008 to June 2009, said a report by the U.N. High Commissioner for Human Rights.

A separate report by the U.N.'s rights office said that, in at least 27 attacks on villages in southern Sudan, the Lord's Resistance Army killed more than 80 civilians and kidnapped many others to use as child soldiers, sex slaves and spies.

The report called the attacks in Sudan, which it said took place between December 2008 and March 2009, deliberate and brutal.

Both reports were based on hundreds of interviews with survivors and several field trips to the remote areas by U.N. employees, said Rupert Colville, spokesman for the high commissioner.

One survivor in Sudan told U.N. employees that he found the mutilated body of a fellow villager.

"The villager's leg had been chopped off, his jaws had been dislocated and his teeth had been pulled out," the report said.

The rebels frequently cross into Congo and Sudan and are notorious for mutilating and murdering civilians and kidnapping children to use as fighters.

Survivors in Sudan told U.N. investigators that armed Lord's Resistance Army rebels arrived in groups of between five and 20, and attacked people with axes, bayonets, hoes, knives and machetes. They reserved the use of firearms for those who tried to flee, the report said.

The LRA attacks in Sudan may amount to crimes against humanity, while the widespread abuses in Congo may have been war crimes as well, it said.

A spokesman for the rebel group, David Matsanga, denied the allegations in the U.N. reports and called it false and malicious. He said that most of the civilian deaths were caused by the Uganda People's Defense Force, of UPDF, the government's army.

"On many occasions the UPDF and troops from southern Sudan and Congo killed civilians thinking that they were the LRA rebels they were hunting for," he told The Associated Press. "We should not be held responsible for killings made by UPDF and other forces."

Matsanga said the group is tired of fighting and looking for lasting peace.

But, a Sudanese woman who escaped after being abducted by LRA rebels said female captives were regularly mistreated and raped.