UNITED NATIONS (AP) _ Rebels used looting, killing, violence against women and cannibalism as ``premeditated tools of war'' in northeastern Congo, according to a new U.N. report.

U.N. investigators took testimony from over 500 people during their mission to look into acts of cannibalism and other human rights abuses that took place between October and December in the area between the northeastern towns of Mambasa and Beni.

According to the investigators from the U.N. peacekeeping mission in Congo, 173 killings and executions were reported including 12 incidents of cannibalism. The report was released Thursday.

When rebels took the town of Mambasa on Oct. 12, there were ``massive rapes, as well as systematic lootings, destruction of health infrastructures and forced labor,'' the report said. It named the two rebel groups as the Congolese Liberation Movement and the Congolese Rally for Democracy-National.

The first murders occurred at the end of October when the Congolese Rally for Democracy-Liberation Movement was counterattacking.

``Bodies were mutilated and left in public places as a strategy to terrorize the population,'' the report said.

At the end of November, when rival groups took back Mambasa and advanced toward Beni at the end of November and in December, systematic looting continued along with frequent rapes and there was systematic violence against Pygmies, forcing them to flee from the forest, it said.

``The testimonies of 503 persons ... indicate a pattern of looting, killing and violence against women used as premeditated tools of war,'' the investigators concluded.

Most acts of cannibalism ``seem to have been committed with the aim of taking revenge on the Nande and Pygmy populations perceived as assisting and supporting the (Congolese Rally for Democracy-Liberation Movement) authorities,'' they said.

``The acts of cannibalism, preceded by corporal mutilations and sectioning of internal body parts, particularly concerning the Pygmies' internal body parts such as the heart and the liver, can be considered to be pure fetishism aimed at helping the perpetrators to acquire the capacity and ability of the victims to hunt and live in the forest,'' the report said.

The investigators said Congolese Liberation Movement president Jean-Pierre Bemba, at a Feb. 13 meeting in Gbadolite, confirmed their findings of summary executions, rapes, ill-treatment and looting _ but not cannibalism. But the movement refused to allow investigators to interview soldiers in confidentiality.

Bemba is now one of Congo's vice presidents under a power-sharing deal.

The United Nations is building up its forces in volatile northeastern Congo where fighting is killing innocent people ``virtually every day,'' the head of the U.N. mission in Congo said Thursday.

``It's terrible, none of it can be justified ... it's innocent people who are dying, it's not people with guns,'' William Swing, the U.N. secretary-general's representative in Congo, said in a telephone call to Nairobi from Kinshasa, Congo's capital. ``We continue ... to deploy more of our resources eastwards.''

The U.N. Security Council has voted to raise the limit on the number of U.N. troops in Congo to 10,800 and give the force a more robust mandate so it can attempt to stop violence in Ituri, as well as neighboring North Kivu and South Kivu provinces.

There are now around 6,000 U.N. soldiers in Congo, including 800 unarmed military observers, and until now they have been permitted to shoot only in self-defense.