GENEVA — A report detailing hundreds of gruesome attacks against civilians in Congo over a 10-year period won't be released until October, the UN's top human rights official said Thursday, after Rwanda angrily protested the findings in a draft version.

Drafts of the report -- circulated to governments earlier this year and leaked to the media last week -- accused Rwandan troops and rebel allies tied to the current Congolese president of slaughtering tens of thousands of Hutus in Congo in the 1990s.

Rwanda has reacted angrily to the claim that this may have constituted genocide or crimes against humanity, and threatened to pull its troops from UN peacekeeping missions if the report was published unchanged, claiming the five-year study was "fatally flawed" and "incredibly irresponsible."

UN High Commissioner for Human Rights Navi Pillay said in a statement that the report will now be released Oct. 1 in order to allow affected governments time to publish their comments alongside the final version.

"Following requests, we have decided to give concerned states a further month to comment on the draft," she said. "I have offered to publish any such comments alongside the report itself."

Rwanda, a small country in East Africa, contributes thousands of soldiers to peacekeeping missions in Chad, Haiti, Liberia and Sudan. It would create a headache for the United Nations if Rwanda made good on its threat and withdrew its troops.

UN Secretary-General Ban Ki-moon on Thursday praised Rwanda's participation in peacekeeping missions, saying the United Nations was "very grateful for such strong support."

"I sincerely hope that such support and contribution will continue for peace and security in the region," he told reporters in Vienna. "The peace and security in Darfur and Sudan ... has very important implications for peace in (the) wider region."

A spokesman for Pillay denied Tuesday reports that Ban had put pressure on the organization's human rights chief to remove references to genocide from the text.

Nevertheless, the report could prove embarrassing for Rwandan President Paul Kagame, an ally of the United States and Britain whose government has long claimed the moral high ground for ending the 1994 genocide of Tutsis that also included the killings of some moderate Hutus.

The report, which cost $3 million to produce, details more than 600 incidents of human rights abuses in eastern Congo between 1993 and 2003 in which tens of thousands of people -- mostly women and children -- were killed.

"Over 1,280 witnesses were interviewed to corroborate or invalidate alleged violations, including previously undocumented incidents, and more than 1,500 documents were collected and analyzed during the two years that it took to research and write the report," Pillay's office said.

The aim was to propose to Congo's government ways in which it can bring the perpetrators of crimes to justice and assist survivors, Pillay's office said.