The Ugandan army says at least 10 of its soldiers were ambushed and killed in the Central African Republic last month while chasing Lord's Resistance Army rebels.
Ugandan newspapers report the army chief has ruled out an attack by the LRA, placing the blame instead on Sudanese militiamen.
The chief of defense forces, General Aronda Nyakairima, confirmed reports that the attack occurred on May 27 but he said the LRA is no longer capable of attacking Ugandan forces.
The general said the attackers were probably armed men from Sudan on a hunting expedition.
Ugandan forces have been pursuing LRA fighters across the CAR, southern Sudan, and the Democratic Republic of Congo since December 2008.
The Ugandan offensive has scattered the LRA from its former bases in Congo but the U.N. and various human rights groups say the rebels continue to attack villages and conduct massacres across central Africa.
The LRA is notorious for abducting children to use as soldiers and sex slaves and mutilating civilians to terrorize local populations.
Four of the group's leaders, including its chief Joseph Kony, are wanted by the International Criminal Court for war crimes.
The rebels fought the government of President Yoweri Museveni in Uganda for nearly two decades before evolving into a regional threat.