Lawyers from Burundi have appealed for action to be taken by the International Criminal Court on behalf of 60 families who say their relatives were killed in government extrajudicial executions.
Hundreds have been killed and almost half a million people have fled Burundi since President Pierre Nkurunziza's controversial decision last April to run for a third term.
"Members of the Burundian state apparatus have murdered Burundian citizens with impunity," read a statement from the lawyers, who include Armel Niyongere, a key civil society leader.
The appeal, sent to The Hague-based ICC as well as to the UN High Commissioner for Human Rights, Zeid Ra'ad Al Hussein, was filed on behalf of the families "in order to bring the perpetrators of these grave crimes against humanity before the courts."
ICC prosecutor Fatou Bensouda said in November that she was ready to act if wide-scale abuses were committed in Burundi.
Burundi's government has rejected reports of extrajudicial executions, blaming violence on rebels and gunmen.
The lawyers said they wished to gather evidence about the killings to build a case for trial.
The ICC was set up in 2002 to investigate and try those responsible for genocide, war crimes and crimes against humanity, where national authorities cannot or will not prosecute.
"The motivation of the families is to fight against impunity and to bring in front of the courts those who participated in these crimes, regardless of their current position in the Burundian state apparatus," the lawyers added.
Last week, the UN rights chief said reports of torture had increased in Burundi since the beginning of the year and many people there now "live in terror."