Armed men attacked the home of an African Union peacekeeper in Darfur's main town of el-Fasher, causing deep concern over the safety of the 7,000-strong mission in western Sudan, an AU spokesman said on Friday.
"Four unidentified armed men dressed in civilian clothes attacked the residence of an (AU) civilian officer," Noureddine Mezni said of the assault on Thursday just outside the AU's main headquarters in el-Fasher town.
"They tied him and his guard up and they stole his vehicle and his cellular phone," he added. The men were not injured.
The AU has had 91 vehicles stolen since its mission in western Sudan began in 2004.
Numerous attacks on AU personnel in remote areas of Darfur have halted some of the mission's operations such as patrols. The attack in el-Fasher, the heart of the operation, is likely to further disable the ill-equipped and cash-strapped force.
The mission has struggled to stem the rape, killing and pillage in Darfur which has killed an estimated 200,000 people and driven 2.5 million from their homes in four years.
Washington calls the violence genocide, a term Khartoum rejects and European governments are reluctant to use.
The International Criminal Court has said it suspects at least two people, a government official and militia leader, of responsibility for war crimes in the vast region bordering Chad, which has also suffered as the conflict spilled over the long and porous border.
Mezni said the acting head of the AU mission in Khartoum had contacted government officials at the highest level to express deep concern and to attain assurances for the safety of the AU personnel in el-Fasher town.
"(She) alerted the authorities to catch the criminals and recover the vehicle," Mezni said. "This is of deep concern for the (AU) leadership."
Attacks on the AU and aid workers in the world's largest humanitarian operation in Darfur have largely gone unpunished and the perpetrators are rarely caught.
The government says security is good in Darfur except in rebel-controlled areas and that the Western media exaggerates the conflict. Khartoum rejects a UN Security Council resolution authorising a 22,500-strong U.N. peacekeeping mission to take over from the AU.
Sudan has also stymied a compromise hybrid U.N.-AU force in Darfur, although a few U.N. personnel have been deployed to help the AU with logistics.