A Ghanaian military peacekeeper in Sudan's Darfur region has been killed.The officer was killed at the weekend by unidentified Darfur gunmen who hijacked his car within yards of the peacekeeping mission's headquarters.Reports say the officer was traveling alone in his vehicle when he was ambushed.Colonel W.E.K. Nibo, the Director of Public Relations of the Ghana Armed Forces told Joy News the family of the deceased was yet to be informed of the loss and until then the army will not want to disclose his identity.He said intelligence reports are yet to uncover what the motive was but it has been established that some unknown armed elements were responsible for the shooting of the officer.The ambush took place hours after the 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 U.N. troops in Darfur to reinforce the AU mission.It was the third slaying of an AU peacekeeper this month. AU spokesman Noureddine Mezni says if this growing hostility continues, truly the AU mission will be compromised and the necessary measures would have to be taken.The latest attack brings to 18 the number of peacekeepers killed in Darfur. An AU officer is also being held hostage since being kidnapped in December.