Seventy-nine "enemies" and eight government soldiers died during and after Friday's coordinated attacks on three military bases in Burundi, an army spokesman said Saturday.
"The final toll of the attacks yesterday is 79 enemies killed, 45 captured and 97 weapons seized, and on our side eight soldiers and policemen were killed and 21 wounded," said Colonel Gaspard Baratuza.
The army on Friday said that 12 rebel gunmen had been killed and 21 captured, but on Saturday morning residents of different neighbourhoods of Bujumbura awoke to find at least 39 corpses lying in the streets.
"Fighting continued into the night and the corpses found in these neighbourhoods this morning are enemies," said Baratuza.
Several witnesses accused soldiers and police of extrajudicial killings, describing security officers breaking down doors to homes, dragging out young men and executing them.
Some of the victims had their arms tied behind their backs while others were killed at close range, according to witnesses.
The army spokesman declined to comment on the details of the fighting and deaths.
The government collected the bodies from the streets of Bujumbura on Saturday and sources said they were swiftly buried in mass graves in the afternoon, "to prevent the spread of disease."
But some residents accused authorities of trying to hide evidence of massacres perpetrated by the security forces.
This week's violence is the worst since a failed coup attempt in May, sparked by President Pierre Nkurunziza's bid for a third term which he won in July's elections.
Hundreds have been killed in protests, armed attacks and assassinations since the unrest began in April and more than 200,000 have left the country, according to UN figures.