"As we speak, we have had to suspend action in many areas. Tens of thousands of people will not get any assistance today because it is too dangerous, and it could grow," Egeland told a news conference in Geneva, Switzerland.

Noting that Darfur was a continuing crisis in spite of very effective humanitarian work, Egeland said the level of violence had escalated sharply in September.

If the violence continued to escalate and it continued to be so dangerous to unarmed humanitarian workers, the UN might not be able to sustain its operations for 2.5 million people requiring life-saving assistance there, he added.

He hailed some 11,000 humanitarian workers on the ground in Darfur and donors, saying the UN had received generous contributions from the United States, the European Union and other countries.

The conflict in Darfur pits Sudanese government troops and allied militias like the Janjawid against two main rebel groups, the Sudan Liberation Movement/Army (SLM/A) and the Justice and Equality Movement, which claim to be fighting the marginalisation of their region by the Khartoum-based government.

According to the UN, more than 2.9 million people continue to be affected by the conflict, of whom 1.85 million are internally displaced or have fled to neighbouring Chad.

Asked if he thought the rebels and the government-allied Janjawid militias still shared the blame for the strife in Darfur, or if it had shifted more to the rebels and bandits, Egeland said all parties to the conflict were to blame for the crisis, and incidents of banditry would continue to increase if the conflict persisted.

He added that he hoped all the parties involved in the conflict would behave responsibly and reiterated that humanitarian operations in Darfur must be maintained.

African Union troops or some other force needed to be boosted to three times the strength of the current peacekeeping force, Egeland added.

He said there was also a need for a political agreement in Abuja, the Nigerian capital, where peace talks between the Sudanese government and representatives from Darfur's rebel groups were under way.

Asked who the main attackers in Darfur now were, Egeland said the recent raids were sometimes attributed to rebels or guerrilla forces. Others were blamed on a splinter group of the SLM/A, while the Janjawid was responsible for some of the attacks.

Government forces also bore responsibility for some of the violence and there were also ethnic militias and armed bandits involved, he added.

He noted that the world had a false impression that things were currently going reasonably well in Darfur and attention had wandered elsewhere. Violence, he stressed, had continued.