Two of the three people killed overnight were civilians who died in grenade attacks by people thought to be working with the police, according to Pierre Claver Mbonimpa of the Association for the Protection of Human Rights and Incarcerated Persons (APRODH). However, local official Esperance Ngerageze told the DPA news agency that the two victims were shot dead.

"Investigations are still under way," he said.

The third person killed is reported to have been a soldier, who was shot dead while trying to arrest a fellow soldier for throwing a grenade at a house.

Human rights groups say more than 70 people have been killed in the violence that has plagued Burundi since April, when President Pierre Nkurunziza announced that he intended to seek a third term on July 15.

The opposition, which has said it will boycott both the presidential vote and the parliamentary election scheduled for Monday, argue that the Nkurunziza is barred by the constitution from seeking a third term.

Parliamentary speaker flees

Among the most prominent figures to oppose the president's plans is the speaker of the National Assembly, Pie Ntavyohanyuma. He announced on Sunday that he had left Burundi and would remain abroad indefinitely.

"I was forced to quit the country due to the unrest caused by the president's insistence to seek a third term bid which is illegal, which is unconstitutional," Ntavyohanyuma told French broadcaster France 24 from Brussels.

"I personally advised President Nkurunziza to drop his plan for a third term, but his answer was to threaten me, to humiliate me," he added.

In view of the ongoing violence, Burundi's authorities have faced widespread calls from the international community, including the European Union, the United Nations and the United States to postpone the elections. However, the elections have already been postponed once and talks between rival political factions on a proposal for put off them off for a second time broke down without agreement.

Despite the lack of security, and the fact that an estimated 127,000 people have fled the country as a result, Burundi's national election commission said on Sunday that everything was in place to go ahead with the parliamentary election on Monday.

pfd/ng (Reuters, dpa, AFP)