Sudan's authorities are planning to move Darfur's displaced civilians back to their villages from the camps where they have sought refuge.
Government officials are being accused of arming the Janjaweed
Many of the displaced are reluctant to return home, as they fear they will be killed there by Arab militias.
The government insists no one will be forced to leave the camps.
Meanwhile it cast doubt on the authenticity of documents, held by human rights groups, which allegedly show Khartoum is backing the militias.
The Janjaweed are accused of killing thousands and using mass rape against non-Arabic groups.
US Secretary of State Colin Powell said the international community was "completely dissatisfied" with the security situation in the region.
"The situation remains very, very serious, and first and
foremost, the security has to be dealt with," he said.
"Not enough is being done to break the hold of the Janjaweed.
Rapes are still occurring. People do not feel safe leaving the camps
to go out and forage for food."
The New York-based organisation Human Rights Watch says it has government documents showing that officials directed recruitment, arming and support of the Janjaweed.
One from the deputy interior minister is alleged to ask for the recruitment of "knights" - a reference to militia.
Group director Kenneth Roth said the documents showed that the Sudanese government had lied to Mr Powell and UN Secretary General Kofi Annan when it denied recruiting and arming the militias.
But Sudanese Foreign Minister Mustafa Ismail told the BBC the documents were "90% false".
Afraid to leave
Sudan's government says more than a million people in Darfur's camps need to go back to their villages and get on with their lives.
The displaced people in several camps say government officials have been announcing their plans to move them using loudspeakers in the camps.
Many of the displaced people say they are afraid they will be forced to leave their places of refuge, particularly since large numbers of police are being moved into the camps.
But the government says the police are there to protect the people and that no-one will be forced to go home.
"There will be a voluntary repatriation for them to go back to their villages and now actually thousands of people now are going back to their villages," said Sudanese Interior Minister Abdul Rahim Mohammed Hussain.
"That is happening. In north Darfur, here in west Darfur, it is happening now."
But the BBC's Hilary Andersson in Darfur says in many parts of the region civilians are still flooding into the camps, not out of them.
She says the camps are filthy and overcrowded. There is little proper shelter, disease is spreading - and every day new graves are dug for those who have died of starvation.
Aid agencies warn that thousands more people could die from hunger and disease in the coming months.
On Tuesday, a group of British charities - known as the Disasters Emergency Committee - launched an urgent aid appeal for the people of Sudan.