"The humanitarian situation in Darfur has quickly become one of the worst in the world. Access to people in need is blocked by the parties in conflict and now, as the need for aid grows, stocks of relief materials are dwindling," said Mr. Egeland, who is also Under-Secretary-General in charge of the UN Office for the Coordination of Humanitarian Affairs (OCHA).

Fighting between forces loyal to the Government of Sudan and the main rebel Sudan Liberation Movement/Army (SLM/A) escalated in the Darfur areas last March and drove 670,000 people to join an earlier 200,000 internally displaced persons (IDPs). Some 70,000 of them fled across the border into Chad, where they lack basic supplies, OCHA said.

The Sudanese crisis is already estimated as being the worst worldwide, with 4 million people displaced. The SLM/A has been holding talks with the Sudanese government recently, but the other rebel movement, the Justice and Equality Movement (JEM), has refused to do so.

In the few areas accessible to humanitarian workers, IDPs lack water, food, shelter and sanitation facilities, Mr. Egeland said.

"I remind combatants of their obligation to minimize the impact of their hostilities on civilian populations, in accordance with international law," he said.

Access to both rebel- and government-held areas continues to be denied or constrained by restrictions on travel permits and insecurity caused by militia activity and banditry, OCHA said. Trucks carrying aid have been attacked and relief workers held by armed groups.

"I urge the government and the militias to take all possible steps to allow humanitarian workers to safely deliver aid to people who desperately need it. Parties to the conflict should honour the agreement they signed in September, which guaranteed aid workers safe and unimpeded access to people in need," Mr. Egeland said.