Two days of fighting between Ugandan forces and a tribal militia in a remote district near the border with Congo have left at least 19 people dead, a Ugandan government official said Sunday.

After the 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, government spokesman Col. Shaban Bantariza said.

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The killings are an escalation of a long-running conflict between Ugandan security forces and rebels who are believed to be loyal to a tribal king, Wesley Mumbere, a critic of the country's long-time president.

Mumbere is king of Uganda's Bakonzo people, and some of his supporters have been calling for secession from Uganda, according to Bantariza, who said he had seen copies of money printed by the secessionist group, which is hoping to create a republic known as Yiira.

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

Some of the rebels had climbed high up the Rwenzori mountains and set up military camps from which they were said to run a small government, even collecting taxes from the people they control. The rebels are armed with modern weapons and improvised explosive devices, according to Bantariza.

"They had shut down life in the areas they occupied," he said. "We shall beat those who want to cause trouble on our land."

Museveni, in power since 1986, has struggled to win over the support of the Bakonzo people in presidential elections. There are frequent land disputes in the area, with many accusing the government of sponsoring land grabs. A new plan to divide up Kasese into two parts has also been fiercely opposed.

In the 1990s, the area was the scene of a violent insurgency by the Allied Democratic Forces, a rebel group that now is based in Congo after being forced out of Uganda.