A convoy of Nigerian pilgrims on their way to Mecca was attacked as it drove through the war-torn Darfur region of western Sudan. The African Union suspects rebels were responsible for the violence.

According to the African Union, seven Nigerian Muslims were killed and eight wounded after rebels fired them on them earlier this week.

The group was heading to the holy city of Mecca in Saudi Arabia when they were ambushed earlier this week.

One rebel group, the Justice and Equality Movement, has denied responsibility for the attack.

"Our troops doesn't ambush anybody on the ground," insisted Omar Adam, the commander of the group. "We haven't any information about that."

The other rebel group, the Sudan Liberation Army, could not be reached for comment.

The AU official said one of the trucks had been looted. He said this was the fourth attack in the last few weeks against Nigerian Muslims heading to Mecca.

The fighting, pitting local rebel groups against government-backed militias has claimed tens of thousands of people and displaced close to two million people.