Unidentified Darfur gunmen killed an African Union officer from Ghana and hijacked his car within meters of the peacekeeping mission's headquarters, the AU said Sunday.

The officer was traveling alone in his vehicle when he was ambushed late on Saturday, said AU spokesman Noureddine Mezni.

The ambush took place hours after US Deputy Secretary of State John Negroponte visited the AU headquarters in El Fasher as part of a trip to Sudan to push the government to allow UN troops in Darfur to reinforce the overwhelmed AU mission.

It was the third slaying of AU peacekeepers this month.

"If this growing hostility continues, truly the (AU) mission will be compromised and we will have to take the necessary measures," Mezni told said on the telephone.

Mezni and other AU officials said they did not know the identity of the gunmen, but would investigate the killing, which took place on the outskirts the government-controlled town of El Fasher in North Darfur, where the 7,000-strong AU mission has its headquarters since deploying to Darfur in 2004.

"More than 90 vehicles have been hijacked since the beginning of the mission," Mezni said.

He accused certain Darfur fighting factions of trying to "drag the AU into the conflict".

"This cannot happen," he said. "We came here to protect civilians. If this is becoming impossible, we will take appropriate measures," he said.

The latest attack brought to 18 the number of peacekeepers killed in Darfur, and an AU officer is also held hostage since being kidnapped in December.

Last week, three soldiers from Rwanda's contingent to the AU mission were killed and an AU car hijacked during a patrol in North Darfur, which took place in a zone controlled by the Sudan Liberation Movement rebels, the AU said.

Two other injured Rwandans were medically evacuated in critical condition.

Earlier this month, five Senegalese peacekeepers were slain in an ambush earlier, which occurred a day after a general acting as the AU's deputy force commander narrowly escaped being gunned down in his helicopter as he was heading to a meeting with rebels.

There are also almost daily reports of vehicles being hijacked, aid workers assaulted and refugees harassed throughout Darfur. Vast sectors of the region, nearly the size of Texas, are off limits to the peacekeepers. But the Sudanese government opposes a plan by the United Nations to replace them with a 22,000-strong UN force.

However, Sudan and the UN are now edging toward a compromise deal that would allow some 3,000 UN troops to deploy in Darfur as reinforcement to the AU.

(China Daily via agencies April 16, 2007)