Arab militiamen responsible for atrocities in Sudan's Darfur region are now guarding camps for the displaced, a UN official has been told by refugees.
The Arab militia are accused of ethnic cleansing in Sudan
Refugees in different camps in North Darfur have said this to United Nations High Commissioner for Human Rights Louise Arbour, she told the BBC.
The militiamen have been recycled into Sudan's police force, she said.
The UN is threatening to impose sanctions on Sudan's oil industry, unless it stops the violence in Darfur.
The Sudanese government denies backing the Janjaweed militia and blames the violence on two rebel groups, who took up arms last year, accusing the government of ignoring the region.
More than a million black Africans have been driven from their homes in Darfur and up to 50,000 killed.
Enlarged African Union (AU) monitoring force
UN to investigate claims of genocide
Threatens Sudan with oil sanctions if it does not disarm the militias and protect civilians
Sudan to submit the names of militiamen and others arrested for human rights abuses
All Sudanese parties to stop human rights violations
"They claim to see former Janjaweed... recycled into the police," Ms Arbour told the BBC's Today programme.
"There is a widespread belief they are being protected by their very oppressors."
The refugees have always said that the Janjaweed worked in conjunction with the security forces to force them from their homes.
The government has responded to international pressure to end the violence in Darfur by sending thousands of extra police officers to the region.
Ms Arbour also accused the government of not doing enough to protect the refugees, first denying abuses were taking place and then saying it is too difficult to identify those responsible.
"There is a total sense of impunity," she said.
'Honour the ceasefire'
UN Secretary General Kofi Annan called for broader backing for peacekeeping efforts in Darfur in his address to the world body's General Assembly on Tuesday.
"Let no one imagine that this affair concerns Africans
alone," he said.
"The victims are human beings, whose human rights
must be sacred to all of us. We all have a duty to do
whatever we can to rescue them, and do it now."
US President George W Bush also drew attention to Darfur in his speech to the assembly, calling on Sudan "to honour the ceasefire it signed".
Human rights group Amnesty International has meanwhile called for the number of African Union peace monitors in Darfur to be increased.
The number of monitors should be increased from its current strength of a few hundred to about 10,000, Amnesty spokesman Samkelo Mokhine said.
Proposals for beefing up the number of African Union monitors in the region were included in the recent UN resolution on Darfur.
Sudan has said it will comply with the latest UN resolution but said it was "unfair" and gave the rebels an incentive not to reach a peace deal with the government.
Talks between the Sudanese government and rebels ended without agreement in Nigeria on Friday.
The rebels refused to sign an accord on greater access for aid agencies, saying pro-government militias must lay down their weapons first.