The top United Nations envoy for the prevention of genocide charged Monday that Arab militias have escalated their campaign of violence against civilians in the Darfur region of Sudan, mounting an unprecedented pair of attacks against camps for displaced families.

Juan Mendez, special adviser to U.N. Secretary General Kofi Annan, said Khartoum has not abided by a long-standing Security Council order to establish a "plan to disarm" the Sudanese-backed Arab militiamen, who stand accused of driving more than 2 million tribal Africans from their homes since 2003.

"I found the situation much more dangerous and worrisome than I expected it to be," said Mendez, who just completed his second visit to the region in the past year. "Until last week, there have never been concerted, massive attacks of an indiscriminate nature against civilians" in camps in Darfur.

Mendez also told reporters that governments have an obligation to cooperate with the International Criminal Court, which has begun an investigation into alleged war crimes in Darfur. The United States opposes the Hague-based court, which it believes may conduct politically motivated investigations into U.S. military actions. Congress has also passed legislation that limits U.S. cooperation with the court.

Mendez's news conference came shortly after he presented a report on his findings to the U.N. Security Council. Mendez had hoped to brief the council personally but was prevented from doing so by the United States and Sudan's three closest allies on the council, Russia, China and Algeria.

U.S. Ambassador John R. Bolton said the Security Council, which received a briefing about Darfur from a senior U.N. peacekeeping official Monday, has sufficient evidence of abuse to take action. He said another briefing on the matter would distract the 15-nation council from making decisions needed to halt the violence.

"We should talk about next steps, not about how to arrange the furniture in the Security Council," Bolton said.

Another senior U.S. official said that Bolton, a fierce opponent of the International Criminal Court, was not trying to block a discussion of the tribunal.

France's U.N. ambassador, Jean-Marc de La Sabliere, said he "strongly regrets" that Mendez was "not authorized" to speak to the council despite a personal appeal on Friday from Annan: "The majority of delegations wished to hear what Mendez had to say, but four delegations were opposed."

In an unrelated action, the Congo Republic, Ghana, Peru, Qatar and Slovakia were elected to two-year seats on the Security Council.