Large numbers of Burundians have fled to neighbouring countries such as Tanzania. Photo: Oxfam
By BBC News
The UN secretary-general has condemned "inflammatory rhetoric" amid growing concern at the escalating violence in Burundi.
The Brussels-based International Crisis Group says the language is "chillingly similar" to that used in Rwanda before the genocide of 1994.
President Pierre Nkurunziza has issued an ultimatum for gunmen to lay down their weapons this weekend.
The violence began in April when the president said he would stand again. He argued that his first term as president did not count towards the constitutional two-term limit as he was chosen by MPs.
Mr Nkurunziza was duly re-elected to a third term with 70% of the vote in July. This weekend's weapons ultimatum has led to a spike in killings.
In a statement, UN Secretary-General Ban Ki-moon said the discovery of bodies in the Burundian capital, Bujumbura, was now a regular occurrence - and many victims showed evidence of summary execution.
Mr Ban said Burundian authorities had a responsibility to protect civilians. France has called for an urgent UN Security Council meeting to discuss the crisis.
The International Crisis Group and others were commenting on remarks by Burundi's Senate President Reverien Ndikuriyo - who threatened to "pulverise" opponents who did not lay down arms.
Thomas Perriello, the US special envoy for the Great Lakes region, told the BBC it was not too late for Burundi to seek a peaceful resolution to the conflict:
"There is still time for [peace talks], though obviously the language of ultimatums, the language of 'last calls', senior government officials talking about 'exterminating and pulverising' enemies - this is the worst kind of rhetoric to try to de-escalate the situation."
Uganda is leading regional efforts to broker peace talks.