UN Secretary-General Kofi Annan warned the Sudan government that its restrictions on vital supplies and relief workers distributing them in Darfur constituted a violation of international humanitarian law.

In a report sent to the UN Security Council on Monday, Annan also said atrocities, including rape, pillaging and driving people from their homes, were swelling the population in squalid camps, now about 2,5-million.

Despite a May 5 peace agreement between Sudan's government and some rebel groups, Annan made clear that people had not reaped any gains yet, despite efforts by the African Union, which negotiated the pact and whose monitors and troops are the only bulwark against atrocities in Darfur.

Humanitarian access has been limited by the Khartoum government's refusal to allow foreign aid groups to hire national staff. Officials have also harassed UN staff about travel documents, especially in areas held by the rebel Sudanese Liberation Army in south Darfur.

"At the same time, government-imposed embargoes on certain essential items, including fuel, foodstuffs and other humanitarian assistance entering SLA-held areas in South Darfur, have prevented the access of civilians to vital goods and constitute a violation of international humanitarian law," Annan wrote in the 10-page report.

While he put much of the blame on the government and Arab militia supporting it, the rebels, who have broken into splinter groups, have hijacked relief trucks and forced four assistance groups to suspend food distribution.

As a result, 80 000 people have currently no access to vital services, around 1 000 children per month no longer receive routine vaccinations, and a polio immunization campaign had to be suspended for 20 000 children under the age of 5, Annan said in the report.

In the camps themselves, government attempts to assert control have "contributed to an atmosphere of intimidation and volatility" with camp residents "viewing the Sudanese police with increasing suspicion and even open hostility."

Sudan, despite a special court to try crimes against civilians in Darfur, has done little to prosecute high-ranking state officials and leaders of armed groups and militia. The court, Annan said, has heard only one case so far.

"The lack of a good faith effort to investigate and hold individuals accountable for war crimes, crimes against humanity and other offenses reinforces a widely shared sense of impunity," the report said.

Rebels took up arms in early 2003, accusing the Arab-dominated central government of neglecting Darfur.

Khartoum backed so-called Janjaweed militias, drawn from Arab tribes, to crush the rebels. A campaign of murder, looting, rape and arson ensued.

Jan Egeland, the UN emergency relief coordinator, warned last week that foreign aid efforts face collapse in Darfur unless donors contributed more funds and the African Union force was beefed up so it could provide more protection.

"I therefore repeat my urgent appeal to the international community to continue supporting the humanitarian effort for Darfur in this critical phase of implementation of the Darfur Peace Agreement," Annan said, adding that "not a single day can be lost in this regard."