Claver Nduwayezu, better known as Carmel or Mukono, is a former commander from the National Liberation Forces rebel movement led by Agathon Rwasa.

Nduwayezu was incorporated into Burundi's regular army after a ceasefire in 2008, but went back into the bush after the 2010 elections that were boycotted by the opposition.

"The notorious Carmel alias Mukono had been in hiding in the DRC for some time," Domitien Kabisa, the military commander in charge of a region bordering on the vast central African country, told journalists.

"He was ambushing vehicles on the road between Uvira and Bukavu on Tuesday night. The Congolese army intervened and they killed Mukono in the ensuing clashes," he went on, adding that the body of the rebel chief had been handed over to the Burundian army early Wednesday.

"It's a great victory because we've just neutralised one of the people bearing the greatest responsibility for the unrest we've seen since 2010," a government official told AFP, asking not to be named.

Nduwayezu has been accused of being the brains behind the massacre of some 40 people in a bar in the border village of Gatumba in September 2011. Later that year the public prosecutor's office issued an international warrant for Nduwayezu's arrest.

A surge in violent incidents since the 2010 elections has led some observers to fear that Burundi, which is still struggling to emerge from 13 years of civil war, could be heading back into all-out conflict.