Darfur militiamen ambushed and killed at least one member of a joint U.N.-African Union (UNAMID) peacekeeping mission and wounded 23 others, a UNAMID spokeswoman said on Wednesday.

"The figures that we have that are confirmed . one person dead and 23 wounded including six who are severely wounded and will be evacuated to Khartoum," Shereen Zorba told Reuters.

Six other personnel were still missing, she added.

Zorba said the UNAMID soldiers and police were ambushed on a routine patrol by around 30 vehicles full of armed militia in the Um Haqiba area of North Darfur on Tuesday. It was not immediately clear if the militias were government allies or backed by rebels fighting Khartoum.

"The mission is obviously outraged by the attack," Zorba said.

Sudan's state news agency SUNA had earlier reported that five peacekeepers were killed in an attack in the western Sudanese region and 17 others were missing.

The ambush is the worst direct attack on UNAMID forces since it began work on December 31.

Arab militias mobilised by Khartoum to quell a revolt by non-Arab rebels in 2003 have been hostile to the U.N. troops in the past fearing they could arrest anyone indicted by the International Criminal Court for war crimes.

While some have since become disillusioned with the government and had turned against it, most have retained their weapons and many have been incorporated into official Sudanese military units.

At full strength, the UNAMID mission would be the world's largest U.N.-funded peacekeeping operation with 26,000 soldiers and police, but it has less than 10,000 personnel on the ground.

UNAMID commanders have urged the international community to provide troops quickly to reinforce the mission. They have also asked industrialised nations to provide vital equipment such as attack helicopters to help restore law and order in Darfur.

The conflict sparked the world's largest humanitarian operation, helping more than 4 million people affected by the fighting. International experts estimate some 200,000 people have died in Darfur.

UNAMID took over at the end of last year from a struggling African Union peacekeeping force which had been targeted by Darfur's warring parties many of whom said the AU was not neutral.

Rebel divisions and ongoing fighting in Darfur has stalled the peace process.