Congolese men in military uniforms have attacked a barge anchored in Lake Albert in western Uganda, killing one person, Uganda's army says.
The barge is owned by Canadian oil company Heritage and was being used to carry out oil exploration in the lake.
A Congolese commander this afternoon confirmed the incident to the BBC but said the Ugandans fired first.
The attack comes just days after the Ugandan army reported four of its troops kidnapped by Congolese forces.
Ugandan army spokesman Lt Tabaro Kiconco told the BBC that the attack took place on Lake Albert between 0100 and 0300 on Friday.
He says a number of Congolese men wearing army uniforms approached the barge in motorboats before opening fire.
One employee of Heritage Oil was killed.
According to the Ugandan army, the barge was anchored in Ugandan waters at the time of the attack.
The Congolese commander says they came under fire from a Ugandan army naval patrol boat and only responded in self-defence.
He also said the two sides were meeting later to try and resolve the issue.
Some factions of the Congolese army operating in the east of the Democratic Republic of Congo are not under Kinshasa's control and various militias and rebel groups also operate freely in the area.
The army and UN are fighting rebel groups in eastern DR Congo
Attempts to integrate one rebel commander and his supporters into the national army earlier this year have backfired.
Tens of thousands of people have been displaced in the last few months by clashes between government troops and other armed groups.
This week's events suggest that the insecurity in eastern DR Congo is threatening to spill over into neighbouring Uganda.
On Sunday, four Ugandan soldiers were kidnapped close to Lake Albert.
Lieutenant Kiconco says the men are being held by Congolese government troops in Bunia in eastern DR Congo and Ugandan authorities are currently negotiating for their release.