KHARTOUM, Sudan — A United Nations peacekeeper who was among a small group of reinforcements sent to Darfur was shot to death at his residence -- the world body's first casualty since its long-negotiated arrival in the troubled region, officials said Saturday.

Gunmen looted the home of the UN peacekeeper -- an Egyptian lieutenant colonel -- in El Fasher, the capital of North Darfur state, and fatally shot him late Friday, the African Union and UN said.

"The senseless killing of an innocent man in the confines of his residence is beyond comprehension," said Hassan Gibril, the deputy head of the AU mission, at a memorial for Lt. Col. Ehab Nazir.

The gunmen who killed him were thought to be burglars, but an official close to the investigation said authorities would not exclude other motives. The official spoke on condition of anonymity because he was not authorized to talk to the media.

In Cairo, the foreign ministry deplored the Egyptian officer's death and condemned in a statement the "sinful aggression" in which Nazir became the "casualty of an attack by armed elements."

The AU has faced increased hostility from warring factions in Darfur, and has lost 19 of its own peacekeepers since it first deployed in June 2004.

"Not a month goes by without a new killing, it's very difficult," said Mezni.

The UN began deploying some 180 staff to Darfur in December to bolster the overwhelmed 7,000-strong AU mission.

This "light support package" is part of a broader agreement that should lead to 3,000 U.N. peacekeepers moving into Darfur in 2007, but the AU and UN both acknowledge that even the first batch of 180 reinforcements have not yet all arrived.

The Sudanese government of President Omar al-Bashir has rejected a U.N. resolution for some 22,000 U.N. peacekeepers to replace the AU in Darfur, where over 200,000 people have been killed and 2,5 million chased from their homes in four years of fighting.

Since then, the Sudanese government, the UN and the AU continue to negotiate a compromise for UN forces to help end Darfur's violence.