The commander of the new hybrid peacekeeping force in Darfur has blamed a breakaway rebel faction for an attack that killed 10 African Union troops.
The Nigerian general with Africa's toughest job
Speaking from the scene of the attack, General Martin Agwai told the BBC it was a splinter group "who broke away from a faction called SLA United".
About 30 AU soldiers are missing and seven were badly injured in the raid, by heavily-armed men in 30 vehicles.
UN Secretary General Ban Ki-moon said the killings were "outrageous".
General Agwai told the BBC's Focus on Africa the attackers destroyed two armoured personnel carriers, looted equipment and stole ammunition from the AU monitoring group at the base in Haskanita.
He categorically ruled out any involvement by government forces.
The Saturday evening attack on the AU military observers was the worst on its troops since their deployment to the region three years ago.
The AU says 40 of the mostly Nigerian troops are still missing. Seventeen were found on Sunday in a nearby village.
Next year the UN and AU will jointly deploy the world's largest peacekeeping force - 26,000 troops - to Darfur.
It will absorb the current force of 7,000 AU troops, which has been struggling to protect civilians in the region.
Meanwhile, officials in Senegal have warned that the country's force in Darfur could be withdrawn following the attack.
One Senegalese soldier was among the 10 members of the mission killed in the fighting alongside seven Nigerians, a Malian and a Botswanan.
"I did not send people there to die. So I have threatened to pull our troops back. I am not the only one," said Senegalese President Abdoulaye Wade.
Mission to Sudan
Meanwhile, a delegation of notable world figures led by Archbishop Desmond Tutu has arrived in Sudan for talks.
The archbishop is leading a delegation of "elders" that includes former UN envoy to Iraq Lakhdar Brahimi, former US President Jimmy Carter, and Graca Machel, a children's rights advocate and the wife of Nelson Mandela.
The group came together at Nelson Mandela's invitation to find ways to tackle some of the world's toughest problems, such as HIV/Aids, poverty and conflict.
The group is scheduled to meet Sudan's President Omar al-Bashir and opposition leaders in Khartoum on Monday before travelling on to refugee camps in Darfur.
Commenting on the raid, Mr Tutu said: "It just shows how desperate the situation is, how desperately we've got to find a peaceful solution so that incidents of that kind don't happen."
At least 200,000 people have died in Darfur during a four-year conflict and more than two million have been forced from their homes.