Crimes committed by Rwanda's army and Congolese rebels in Congo during the 1990s could be classified as genocide, a leaked draft U.N. report says, a charge that will stir tensions between Kigali and the U.N.

A Congo expert said diplomats were wrangling over whether to include the highly sensitive genocide accusation in the final version of the document.

The report details crimes committed in the former Belgian colony between 1993 and 2003, a period that saw the fall of dictator Mobutu Sese Seko and a five-year conflict involving six foreign armies, including Rwanda's Tutsi-led force. Millions of people died, most from hunger and disease rather than violence.

After quashing the 1994 genocide of 800,000 Tutsis in Rwanda, Kigali's army invaded Congo, ostensibly to hunt down Hutu fighters who had taken part in the killings and then fled into the east of Congo, known then as Zaire.

In the process, Rwandan forces swept the Congolese AFDL rebels of Laurent Kabila to power in Congo. Both forces have been accused of a string of rights abuses against Hutu soldiers and civilians across the country.

The systematic and widespread attacks (against Hutus in Congo) described ... reveal a number of damning elements that, if proven before a competent court, could be classified as crimes of genocide, said the report, seen by Reuters on Thursday.

The extensive use of edged weapons ... and the systematic massacres of survivors after (Hutu) camps had been taken show that the numerous deaths cannot be attributed to the hazards of war or seen as equating to collateral damage.

France's Le Monde newspaper said Kigali had threatened to withdraw peacekeepers from Sudan over the charges, but Rwandan officials were not available for comment to Reuters.

A spokesman for the U.N.'s High Commissioner for Human Rights (UNHCHR), which drafted the 545-page report, said the leaked document was a draft, and had some errors.

ROCKING RWANDA?

The report details some 600 serious crimes committed by various forces from a number of nations but Congo expert and author Jason Stearns said Rwanda comes off worst.

The allegation that the Rwandan army could be guilty of acts of genocide against Hutu refugees will greatly tarnish the reputation of a government that prides itself of having brought to an end the genocide against Tutsis in Rwanda, he said.

The final report is due to be presented next week by the UNHCHR, but Stearns said that there was still debate over the inclusion of the genocide accusation, which risked hurting Rwandan President Paul Kagame, who has just won re-election but faces unprecedented dissent within the Tutsi elite.

While most of the dissenting officers were also involved in these alleged massacres in the Congo, this report could further rock the regime, he said.

The report was intended as a mapping exercise of the most serious crimes committed in Congo, which is still seeking political stability, battling economic woes and debating the future role of U.N. peacekeepers ahead of elections next year.

Congo's President Joseph Kabila, who took over when his father Laurent was assassinated, wants U.N. troops out of the country next year but also regularly calls on them to help his weak army face down local and foreign rebels still active there.

It is intended as a historical document to detail the most serious crimes and provide the Congolese authorities with information that they can use to seek justice.

Congo's last main war, which ran from 1998-2003 and at times turned into a scrap for the vast nation's minerals, inflicted so much damage it became known as Africa's World War.

(Additional reporting by John Irish in Paris and Stephanie Nebehay in Geneva); editing by Andrew Roche)