Government spokesman Colonel Shaban Bantariza said Sunday that after rebels had killed four Ugandan police officers and wounded a soldier, Ugandan forces launched an operation in which at least 15 rebel fighters have been killed.

Bantariza said the rebels are believed to be loyal to a tribal king, Wesley Mumbere, who is critical of Uganda's government.

Mumbere is king of Uganda's Bakonzo people, and some of his supporters have been calling for secession from Uganda.

The western district of Kasese, where Mumbere is based, is a hotbed of opposition to Museveni, who lost there in the last presidential polls.