Armed forces in the Democratic Republic of the Congo (DRC) say they have killed 10 Burundian soldiers after they crossed the border from the neighboring country in hunt for rebels.

The Congolese army made the announcement on Monday, saying the fatalities had occurred in the lakeside town of Uvira in the eastern province of South Kivu last week.

Dieudonne Kajibwami, the provincial military spokesman, said Congolese soldiers opened fire on the Burundian troops when they crossed the border after midnight on Wednesday in pursuit of rebels from the ethnic Hutu National Forces of Liberation (FNL).

Another Congolese army officer, who was speaking on condition of anonymity, however, said of an agreement between Burundi and the DRC that allowed Burundian soldiers to act in pursuit of FNL rebels when they fled to the DRC.

"Normally, there is cooperation between the two armies," the officer said, adding that, "The reason for this glitch" lay in the absence of a military commander and ignorance among the soldiers about "the deal between the two sides.”

The FNL is believed to have about 500 fighters based in South Kivu Province.

The Burundian army has declined to comment on the last week incident.

Burundi witnessed a civil war between majority Hutus and minority Tutsis between 1993 and 2005, which killed around 300,000 people. In September 2006, the Burundi government signed the Arusha peace deal with Hutus.

The country also plunged into turmoil in late April 2015 when President Pierre Nkurunziza, a former rebel leader from the Hutu tribe, announced his decision to run for a third consecutive five-year term.