Burundi's national electoral commission dismissed weeks of violence Sunday and said all was ready a day ahead of key polls in the central African nation that the UN warns should be postponed.

"Everything is ready in the country," election commission chief Pierre-Claver Ndayicariye told reporters Sunday, saying all voting material had been delivered to voting centres, with over 11,000 polling stations across the country.

Three people were killed overnight Saturday, adding to the more than 70 killed in weeks of violence and a failed coup sparked by President Pierre Nkurunziza's bid to stay in power for a third term.

One was shot while another was killed in a grenade blast, according to witnesses. A soldier was killed by accident by a comrade during a raid on a house.

The opposition on Friday said it was boycotting the polls, claiming it is not possible to hold a fair vote, with over 127,000 people having fled into neighbouring countries, fearing further violence.