Burundian authorities have discovered three bodies in a single grave in the capital, heightening concerns about the existence of mass graves in the violence-plagued country.

Burundian security forces on Monday watched as residents dug up a grave that had been suspected to contain up to 30 bodies in Bujumbura's Mutakura neighborhood.

Bujumbura Mayor Freddy Mbonimpa said a former rebel who recently surrendered showed security forces to the grave, but two men paraded before the media as suspects in the apparent killings denied any involvement.

Bujumbura has been wracked by violence since April 2015 when President Pierre Nkurunziza announced he would seek a third term that he ultimately won. Since then hundreds of people have been killed.

Many here blame the spiraling violence on the country's security forces.