A Burundian opposition activist, Pontien Barutwanayo, was on Sunday shot dead in the east of Bujumbura.
A witness said on condition of anonymity that Barutwanayo was gunned down at a bar in Isale, 30 kilometers east of Bujumbura.
He said three other people were injured in the attack.
He identified Barutwanayo as a member of the main opposition National Liberation Forces (FNL) party which boycotted a parliamentary election in June and a presidential ballot a month later.
The witness said violence linked to the controversial election victory of President Pierre Nkurunziza persists in the country.
Nkurunziza’s bid for a third term in office sparked months of violent protests in which about 80 people were killed. Critics said his candidacy violated the Constitution and the 2000 Arusha agreement, which led to the end of a 12-year civil war in 2005.
Meanwhile, Burundi’s National Independent Human Rights Commission (CNIDH), said Nkurunziza’s victory had been followed by explosions and killings in Bujumbura.
It said more than 20 people had been killed, adding that fatalities included people who opposed Nkurunziza’s third term, as well as a former army chief and a former intelligence chief.