Kigali - The UN's secretary general has urged Rwanda not to withdraw its peacekeepers from Sudan over a leaked report saying its troops may have committed genocide.

Ban Ki-moon said he was "disappointed" the draft had been released, after he held talks with President Paul Kagame in Kigali in a bid to ease tensions.

The report accuses Rwandan soldiers of massacring civilians in the Democratic Republic of Congo in the 1990s.

Rwanda says the document is "malicious" and "ridiculous" and wants it amended.

The UN last week delayed publication of the document until 1 October, to give countries more time to comment on its contents.

Mr Ban unexpectedly flew to Kigali on Tuesday to discuss the threat by Mr Kagame to withdraw Rwanda's 3,500 peacekeeping forces.

Rwanda has 3,300 soldiers and 86 police serving with a joint UN and African Union force, Unamid, in the troubled western Sudanese region of Darfur. It is led by Rwandan Lt Gen Patrick Nyamyumba.

Another 256 troops serve with the UN Mission in Sudan (Unmis), which is supporting the implementation of a peace deal between north and south.

After meeting Mr Kagame in the capital, Mr Ban told reporters: "Both the president and I are disappointed that the draft report has been leaked.

Mr Ban said he had commended Rwanda's support of the whole UN agenda and peacekeeping operations in Sudan, and hoped it would continue.

Rwanda is not the only country targeted in the report. Other nations who sent troops into DR Congo, such as Angola, are also mentioned, but Rwanda has come in for the most severe accusations.

UN High Commissioner for Human Rights Navi Pillay has said she will publish their concerns in an annex to the report.