(CNN) A large force of rebels stormed an African Union peacekeeping base in Darfur , killing at least a dozen soldiers and wounding several others in the biggest attack on the mission so far, the AU said Sunday.
More than 50 AU peacekeepers and support personnel are missing in action since the attack on the base in northern Darfur just after sunset on Saturday.
"This is the heaviest loss of life and the biggest attack on the African Union mission," said AU spokesman Noureddine Mezni , who could not confirm the casualty figures because the fighting was ongoing.
Officers in the AU force said 1,000 rebels from the Sudan Liberation Army stormed the AU base in the town of Haskanita just after the sunset fastbreaking meal during the Muslim holy month of Ramadan.
"There is a war going on between the rebels and the government, and the AU is crunched in the middle," said a senior AU officer who asked not to be named because of the sensitivity of the issue.
Darfur rebels have grown increasingly hostile to the AU peacekeepers saying the force is not neutral and favors the government side. There have been several ambushes of AU forces in the past year blamed on the rebels.