Burundi's army is accused of killing dozens of people on December 11, according to Amnesty International.
The rights group says that some of the dead were killed extra-judicially by members of the security forces.
"The violent repression that took place on 11 December represented a dramatic escalation in scale and intensity from previous security operations," the Amnesty report says.
"But the modus operandi of the operations - involving extrajudicial executions, systematic looting and theft, arbitrary arrests and targeting of perceived political opposition strongholds - was not qualitatively different from past practice."
Over 87 people were killed in the violence, with the government saying those killed were responsible for attacks on public installations.
See the full report here.