The Ugandan army is investigating an incident in northern Uganda in which soldiers killed at least three civilians and injured 16 others earlier this week during protests over the killing of a young man.

Investigations are set to focus on why a soldier on patrol shot a teenager on the night of Christmas Day, and how a group was formed the next day to protest the shooting.

Ugandan army spokesman Major Felix Kulayigye explains: "Why was this person shot? Is it true that he was challenged for identification and this person did not stop? Two: we're investigating those that incited the people on the 26th to attack the detachment."

Major Kulayigye says that protesters Monday set fire to an army detachment and soldiers' houses. To stop further destruction, he says, soldiers shot into the air.

He says three protesters were killed.

The violence took place at Lalogi camp, near the northern Ugandan town of Gulu. People had moved to the camp from surrounding areas to seek shelter from attacks by the Lord's Resistance Army, a rebel group that has been terrorizing northerners for almost two decades.

Father Cyprian Ocen is an official with the Catholic Church in Gulu. He went to the scene shortly after the shootings and spoke with protesters and family members of the dead teenager.

He disputes the army's version that the young man was shot because he ran away after being asked for identification.

"The boy was going home with, I think, a girlfriend and the UPDF (army) told him to give to him the girl," he said. "I think the boy did not agree. The army had told him that if you don't give me the girl I will shoot you, and that's what took place - he shot that boy dead."

Father Ocen also denies that protesters set fire to the detachment and soldiers' houses, that soldiers only fired into the air, and that only three people were killed.

"Seven people are confirmed dead and 20 are wounded. So I don't think they shot into the air but they shot into the crowd. And yesterday some were still being looked for - some people had disappeared from the camp and the relatives were still looking for [them], said Father Ocen.

Human rights groups and others have complained that some soldiers sent up to the north to protect people against rebel attacks instead end up attacking local people, a charge the army denies.