"We learnt with utter shock and disbelief of the relentless day-long attack on Khor Abeche by armed militia of the Miseriyya tribe of Niteaga (southern Darfur). (...) We condemn this senseless and pre-meditated savage attack," said the statement signed by AU special envoy to Darfur Baba Gana Kingibe and the UN special representative in Sudan, Jan Pronk.
"They rampaged through the village, killing, burning and destroying everything in their paths and leaving in their wake total destruction with only the mosque and the school spared," it added.
But it gave no details of casualties.
The attack was launched on April 7 by some 200 militiamen on horseback led by Nasir al Tijani, backed up by a group of 150 people hailing from Niteaga, the statement said.
Khor Abeche, which was controlled by the Sudan Liberation Movement, the main rebel group in Darfur, was reportedly attacked because the rebels refused to turn over the bodies of two assailants killed during an earlier militia raid on the village on March 9.
"We expect that Government authorities will also take appropriate action against Al Tijaniwho had in their very presence, repeatedly threatened the destruction of Khor Abeche until he finally did so on April 7," the two envoys said.
"The AU had prepared to deploy its troops in Niteaga and Khor Abeche since April 3, to deter precisely this kind of attack, but was prevented from acting by what can only be inferred as deliberate official procrastination over the allocation of land for the troop's accommodation," they added.
The AU has been trying to mediate an end to more than two years of conflict between Khartoum and ethnic minority rebels in Darfur, which has left some 300,000 people dead and 2.4 million displaced.
The partly political and partly ethnic conflict in Darfur pits two rebel groups from the local population of black African origin against an Arab horseback militia, the Janjaweed, widely accused of major human rights violations.
The displaced people have fled to refugee camps, either internally in Darfur or across the border in Chad.
The Sudan Liberation Movement agreed Monday to resume stalled peace negotiations with the government, retracting earlier conditions it had set for returning to the peace table.