On August 13, 2004, a refugee camp in Gatumba was the scene of one of the largest civilian massacres carried out in Burundi in recent years.

Brigadier-General Germain Niyoyankana, head of the Burundian army, accused Congolese troops of complicity in the killings.

[3] Following the FNL's admission of responsibility for the Gatumba massacre, the Burundian government issued arrest warrants for the group's leader, Agathon Rwasa, and declared its intention to refer the matter to the International Criminal Court.

The United Nations issued a resolution condemning the attack, and the African Union declared the FNL a terrorist organisation.

In October 2005, the FNL issued a statement condemning the Gatumba massacre, denouncing Agathon Rwasa for leading a "descent into hell", and announcing that he had been replaced.