KHARTOUM(July 18,2008) - A U.N.-African Union peacekeeper was shot and killed in Sudan's western Darfur region, a week after militiamen killed seven peacekeepers, a U.N. spokeswoman said on Wednesday.

The peacekeeper for the joint U.N.-AU mission in Darfur (UNAMID) was killed while on patrol in West Darfur, U.N. spokeswoman Marie Okabe told reporters in New York.

The incident took place shortly before 5 p.m. local time and the peacekeeper was Nigerian.

"This was a carjacking. He put up some resistance and got shot," UNAMID's sector commander for West Darfur State, Balla Keita, told Reuters.

UNAMID's spokeswoman in Sudan, Shereen Zorba, condemned the attack, which she said occurred close to the Chadian border, and warned that the peacekeeping force was "stretched to the limit".

"It (the attack) is outrageous and despicable and the consequences are not in the best interests of Darfur.

"We call on the international community to act rapidly to strengthen the force. We need to be strengthened, otherwise we're sacrificing the lives of our men and women in vain," she added.

Last week UNAMID soldiers and police were ambushed on a routine patrol by about 40 vehicles full of armed militia in North Darfur. Seven were killed and over 20 more were wounded.

A senior Security Council diplomat said on Wednesday that in a closed briefing after that attack, U.N. peacekeeping chief Jean-Marie Guehenno gave the council details pointing to links between the militia and the Sudanese government.

Khartoum has denied involvement. Its U.N. Ambassador, Abdalmahmoud Abdalhaleem, has blamed the attack on a major Darfur rebel group, SLM Unity.

No information was available about who carried out Wednesday's attack.

U.N. officials say UNAMID personnel are on high alert after Monday's request by the International Criminal Court chief prosecutor, Luis Moreno-Ocampo, that the court issue an arrest warrant for Sudanese President Omar Hassan al-Bashir on suspicion of masterminding genocide in Darfur.