Sudanese-backed Arab militias continue to terrorize hundreds of thousands of black African civilians with impunity in the Darfur region of Sudan, lending greater urgency to international calls for the deployment of thousands of foreign peacekeepers there, the United Nations' top human rights official said Thursday.

Louise Arbour, the U.N. high commissioner for human rights, told the U.N. Security Council that displaced civilians are routinely harassed and intimidated by government security forces that have been sent to Darfur to protect them. Arbour, a former Canadian Supreme Court justice who just returned from a visit to Darfur, said that local police and courts have failed to respond to reports of violence and rape near camps housing displaced people.

"The government continues to convey neither a sense of urgency nor an acknowledgment of the magnitude of the human rights crisis in Darfur," Arbour told the council in a closed-door session. "In short, my mission came away from Sudan gravely concerned that the government, its security forces -- particularly the police and the judicial system -- are failing the people of Darfur."

Arbour, who was accompanied on her visit by the U.N. special adviser for the prevention of genocide, Juan Mendez, stopped short of declaring the violence genocide, noting that a new commission of inquiry being established by U.N. Secretary General Kofi Annan will make that formal determination. The Bush administration has accused the Sudanese government and the militia of perpetrating genocide in Darfur.

But Mendez told the 15-nation council: "Crimes against humanity, war crimes and breaches of the laws of war have probably occurred on a large and systematic scale. We do not believe that we have turned a corner on preventing further violations, and we must remain vigilant to this end."

The crisis in Darfur began in February 2003, when two rebel groups, the Sudanese People's Liberation Army and the Justice and Equality Movement, launched a series of attacks against government outposts, citing discrimination against the region's black civilians. The Sudanese authorities organized and supported Arab militias, known as the Janjaweed, as they swept through the region, killing tens of thousands of civilians and driving more than 1 million from their homes. The World Health Organization estimates that 6,000 to 10,000 civilians are dying each month from violence and disease.

Nigerian President Olusegun Obasanjo said last weekend that the African Union, which has 380 troops monitoring a shaky cease-fire in Darfur, is prepared to send as many as 5,000 more to help defuse the crisis. But he said that Western governments would have to come up with hundred of millions of dollars to support the mission.

Sudan's foreign minister, Mustafa Osman Ismail, denied that his country's armed forces are involved in the violence in a lengthy closed-door speech to the 15-nation council Thursday afternoon. He said Sudan is struggling to stop the militia. Ismail told reporters after the meeting that Khartoum has agreed to an African Union request to allow more than 3,500 troops, including 1,000 police, into Darfur. Ismail said that they would be given a stronger mandate that would allow them to monitor police activities and to help them ensure the protection of civilians.

John C. Danforth, the U.S. ambassador to the United Nations, said that Sudan would have to do a better job of proving its commitment to stop the violence. "This is a show-me situation," he said. Danforth also challenged assertions by Sudan's president, Omar Hassan Bashir, which were published Thursday in the Egyptian newspaper Al-Ahram, that the United States helped arm and train Darfur rebels. It is "baloney," Danforth said.

But Arbour's report did little to increase support for tougher action by the council, which has twice threatened to consider imposing sanctions on the government if it failed to rein in the militia. China, Russia, Pakistan and Algeria continue to oppose U.S. efforts to threaten sanctions on Sudan. "I don't know why we keep speaking about sanctions," said Pakistan's U.N. ambassador, Munir Akram. "We think it's the wrong direction. We have to evoke more cooperation, and it has to be done in a measured way. We shouldn't go overboard."