At least two people were killed overnight in the Burundian capital Bujumbura, relatives and friends said on Sunday, a day before parliamentary elections were due to be held amid an opposition boycott and fears of violence.

Burundi has been in turmoil since April when President Pierre Nkurunziza said he would seek a third term, triggering weeks of angry protests and unrest. His opponents say the move violates Burundi's constitution as well as a peace deal that ended an ethnically charged civil war in 2005.

The opposition has said it would boycott Monday's vote and presidential elections on July 15. Dozens have been killed in the unrest and the U.N. refugee agency UNHCR says almost 127,000 people had fled to neighbouring states, many citing fears about election-related violence.

In the night to Sunday, a police officer shot and killed a university student in Bujumbura's Jabe neighbourhood while he was returning home from visiting family, his brother said, giving his name only as Alexis for security reasons.

"A policemen who shot at him was close to him. Patrick was stabbed by a bayonet by the same policeman," Alexis told Reuters, still visibly in shock from the killing.

A Reuters witness said loud explosions could be heard during the night in other parts of the city, accompanied by suspected gunfire.

Also in Jabe, another man was killed in a suspected grenade attack, his friend said.

"Someone called him yesterday night during the shootings. He went out and did not return. We ask the government to stop this," said the victim's friend said, giving his name only as Ibrahim.  

Police spokesmen were not immediately available to comment.

VOTE

Talks late last week between rival factions failed to reach an agreement on a proposal to postpone both elections to July 30.

U.N. Secretary-General Ban Ki-moon has said the elections should be postponed due to the prevailing political and security environment, and the United States has also said it was withholding electoral assistance.

Burundi's ambassador to the U.N. has said the vote would go ahead on Monday. The government had already delayed both elections after protests erupted in April.