The UN estimates Darfur's conflict has displaced some two million people
The International Criminal Court's chief prosecutor has compared aspects of the Sudanese government's behaviour in Darfur to that of Nazi Germany.
Luis Moreno-Ocampo said officials were covering up and denying crimes.
"We've seen it before," he told the UN Security Council in comments which were strongly rejected by Sudan.
"The Nazi regime invoked its national sovereignty to attack its own population, and then crossed borders to attack people in other countries."
Sudan's ambassador to the UN said the comments were "fictitious and vicious" and harmful to the prospects of peace.
Mr Moreno-Ocampo 's report comes as UN ambassadors are in Darfur to see the situation.
He delivered his report in New York to those UN Security Council members who have not travelled to Darfur and other African trouble-spots.
He said the "whole state apparatus" of Sudan was implicated in crimes against humanity in Darfur.
"The entire Darfur region is a crime scene. Despite promises and denials over the last five years, millions of civilians have been targeted by officials who vowed to protect them. Impunity reigns. Today we have an historic opportunity to confront those massive crimes," he said.
Explaining his comparisons to Nazi Germany, Mr Moreno Ocampo added: "Sudanese officials protect the criminals and not the victims. Denial of crimes, cover up, and attempts to shift responsibility are another characteristic of the criminal plan in Darfur."
He repeated his earlier call for the council to demand that Sudan hand over two men who face charges of crimes against humanity.
The UN delegation is meeting some of the two million Darfuris who have fled their homes, as well as local officials and members of the under-strength UN-African Union peacekeeping force.
"We really have to see how the people of Darfur live," said South Africa's UN Ambassador Dumisani Kumalo.
Sudanese officials protect the criminals and not the victims
By accusing Sudan's "whole state apparatus" of helping shield criminals, correspondents say, the ICC prosecutor is implicating some of the highest officials of the government, although he does not name any individuals.
The treaty that created the ICC was intended to hold individuals, not entire states, responsible for war crimes and crimes against humanity.
Mr Moreno-Ocampo says the armed forces, intelligence services and the justice system worked together in Darfur, where at least 200,000 people have died in the five-year conflict.
The US has said the killings of black Africans in Darfur amount to a genocide - but the UN has not used that term.
Costa Rica's foreign minister, pointing out the lessons learned from the international community's failure to act in Bosnia and Rwanda, said there had been enough appeasement, and the time to continue accommodating evil had passed.
The Sudanese ambassador to the UN responded angrily that his country would not bend to the will of the ICC.
- In charge of Darfur in 2003 and 2004 as deputy interior minister
- Quoted as saying that he had been given the authority to either kill or forgive in Darfur for the sake of peace and security
- Commanded thousands of Janjaweed in mid-2003
- Allegedly promoted and witnessed rape and torture as part of the war strategy
"We will never submit any of our citizens to be tried in The Hague," Abdalmahmood Abdalhaleem Mohamed said.
"Ocampo is destroying the peace process and we demand that this man be held accountable for what he is doing to the peace process in Sudan."
Sudan has always denied charges that it organised the Janjaweed militias to take revenge on Darfuris, after black African rebels took up arms in 2003.
But Mr Moreno-Ocampo says the pro-government Arab militias are still targeting civilians, who are being bombed, tortured, killed and raped.
He again demanded that Sudan hand over Ali Kushayb, a leader of the Janjaweed militia, and Ahmad Harun, Sudan's current humanitarian affairs minister.
He said Mr Harun had been promoted and was now on a committee overseeing the deployment of UN and African Union peacekeepers.
The two men are charged with 51 counts of war crimes and crimes against humanity, including acts of murder, persecution, torture, rape and forcible displacement.
Both men have denied involvement in war crimes.
Mr Moreno-Ocampo's report states that the ICC is proceeding with two new investigations - one involving government activities in Darfur and the other related to attacks on peacekeepers and aid workers.
He said this included the Darfur rebels alleged to have been responsible for the killing of African Union peacekeepers in Haskanita last year.