Story highlights Four peacekeepers with the African U.N. Mission in Darfur have been killed

They were attacked in El Geneina, West Darfur, the group said

UNAMID says its personnel were fired on and they returned fire

Four peacekeepers with the African Union-United Nations Mission in the Darfur region of Sudan were killed and eight injured in an ambush by unidentified attackers Wednesday, the group said.

The attack in El Geneina, West Darfur, targeted a Nigerian military patrol near the mission's regional headquarters, the group, known by its acronym UNAMID, said. All of the dead were Nigerian, a UNAMID representative told CNN.

One person was airlifted from the scene and is in critical condition, the official added.

Mission personnel were fired on from several directions and they returned fire, the group said in a statement, adding that UNAMID is working with local authorities at the scene.

"The mission condemns in the strongest terms, this criminal attack on our peacekeepers who are here in the service of Darfur's people. I call on the government of Sudan to bring the perpetrators to justice," said UNAMID Force Commander and officer-in-charge Lt. Gen. Patrick Nyamvumba.