A UN report has called for those accused of carrying out war crimes in Sudan's Darfur region to go on trial.
About two million people have been forced to flee their homes in Darfur
The report stopped short of calling the violence genocide, but said the government and its militia allies had killed, tortured and raped civilians.
The report named, in secret, alleged war criminals it said should go before the International Criminal Court.
Sudan rejected the report as unfair and incorrect, while Darfur rebel groups said it did not go far enough.
Correspondents say there is likely to be a fierce debate at the UN Security Council about where any war crimes trials should be held.
The conclusion that no genocidal policy has been pursued and implemented in Darfur by the government should not be taken in any way as detracting from the gravity of the crimes
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The United States does not recognise the ICC and favours the creation of a special court for Darfur instead.
More than 70,000 people have been killed in the two-year conflict and some two million have fled their homes.
Many of the refugees, mostly non-Arabs, say that militiamen backed up by the security forces have ridden into their villages on horses and camels, slaughtering the men, raping the women and stealing whatever they can find.
The Sudan government denies backing the Janjaweed militia and blames the violence on rebels who took up arms in February 2003.
The African Union says some of its ceasefire monitors in Darfur were shot at on Monday while investigating a bombing that the UN blames on Sudan's government.
The Union said it "unreservedly condemns" the attacks, carried out by unidentified assailants in two locations.
Last October, the UN set up the panel led by Italian judge Antonio Cassese to investigate claims that a genocide had been committed in Darfur.
Mr Cassese is the first President of the International Criminal Tribunal for the former Yugoslavia (ICTY).
The other members of the panel are:
- Egyptian Mohammed Fayek
- Diego Garcia-Sayan of Peru
- Hina Jilani from Pakistan
- Ghanaian Therese Striggner Scott.
'No genocidal intent'
Where genocide is found to have taken place, signatories to a UN convention are legally obliged to act to end it.
The panel found that a policy to commit genocide had not been formed but pointed to "killing of civilians, enforced disappearances, destruction of villages, rape and other forms of sexual violence, pillaging and forced displacement, throughout Darfur".
"The conclusion that no genocidal policy has been pursued and implemented in Darfur by the government authorities, directly or through the militias under their control, should not be taken in any way as detracting from the gravity of the crimes perpetrated in the region."
The authors also accused rebel forces in Sudan's western region of committing serious human rights violations which "may amount to war crimes".
Sudan's Justice Minister Ali Osman Yassin said: "The violations indicated in the report were not confirmed and were based on information of a political nature."
He said it was "an emotional rather than realistic investigation", and was "biased and unbalanced".
The leader of one of Darfur's rebel groups told Reuters news agency that he rejected the report's finding that genocide had not been committed.
"There are hundreds of mass graves that the commission did not go to," said Justice and Equality Movement (JEM) leader Khalil Ibrahim.
The United States refuses to recognise the ICC, in case its soldiers are accused of war crimes.
The Janjaweed are accused of widespread atrocities
But most European countries, the UN and lobby group Human Rights Watch believe the trials should take place at the ICC in The Hague.
"This is a case that is tailor-made for the ICC," said Britain's UN ambassador Emyr Jones Parry.
"It's time for the Bush administration to back-pocket its abstract objections to the ICC so justice can be done," said Richard Dicker from the US-based Human Rights Watch.