Recently arrived IDPs in Zam Zam camp, North Darfur.

NAIROBI, 13 Oct 2005 (IRIN) - Continuing insecurity and tension in Sudan's troubled western region of Darfur has disrupted humanitarian work, forcing operations in several areas to be halted, the UN Mission in Sudan (UNMIS) reported on Wednesday.

Almost two-thirds of humanitarian operations in South Darfur State had been suspended, UNMIS said. Recent attacks in North Darfur had led also to the arrival of 6,000 new internally displaced persons (IDPs) into Zam Zam IDP camp.

UNMIS expressed concern over recent African Union reports that white, NGO-type all-terrain vehicles were being used by the government and the rebel Sudan Liberation Movement/Army (SLM/A), UN News reported.

"If true, this might constitute another serious threat to humanitarian actors operating in the area," Radhia Achouri, UNMIS' spokeswoman in the capital, Khartoum, said.

Humanitarian activity had also been hampered in West Darfur, where all roads in and out of El Geneina, the state's capital, had been closed due to armed clashes and banditry.

UNMIS' comments come days after the UN Secretary-General's special adviser on the prevention of genocide, Juan Mendez, said the security situation in Darfur was deteriorating.

"I found the situation much more dangerous and worrisome than I expected it to be," Mendez said on Monday, shortly after a visit to the troubled region.

Fighting in the three states of North, South and West Darfur began when two main rebel groups - the SLM/A and the Justice and Equality Movement - took up arms in February 2003, citing discrimination and oppression of the region by the Sudanese government. The government is accused of unleashing militia - known as the Janjawid - on civilians in an attempt to quash the rebellion.

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