Protesters burned a man alive in Burundi capital on Thursday, saying he was a member of the ruling party's youth wing which had attacked them during their rallies against the president's bid for a third term, a witness said.
Tensions have been building on Bujumbura's streets for almost two weeks between protesters and police using tear gas, water cannon and, demonstrators say, live rounds. The police deny this.
The violence has plunged the African nation into its worst crisis since the end of an ethnically charged civil war in 2005, raising fears of fresh bloodshed in a region still haunted by the genocide in neighbouring Rwanda.
The chairwoman of the African Union bloc's Commission, Nkosazana Dlamini-Zuma, joined government opponents on Thursday in saying the situation had deteriorated so far that the June 26 presidential election should be postponed.
"Until there is peace in Burundi, we can't go for elections," she said on her Twitter feed. President Pierre Nkurunziza's spokesman said that was unnecessary as most of the country was calm.
Protesters said the victim of the burning was a member of the Imbonerakure youth wing of the ruling CNDD-FDD party, which they say has attacked them. The government has repeatedly dismissed charges that Imbonerakure is fomenting violence.
"They put tyres around his neck and then burned him," a witness told Reuters after seeing the man killed in the Nyakabiga district of Bujumbura.