The head of an opposition party in Burundi, Zedi Feruzi, has been shot dead in the capital by gunmen, according to Reuters news agency.
Feruzi and his bodyguard was killed in the Ngagara district according to the head of the civil society group Ligue ITEKA, Anshere Nikoyagize. Residents said he was killed near his home.
"We heard a lot of gunfire," a neighbour of Feruzi told Reuters. "It's unfortunate because there were army soldiers here, and they didn't do anything."
Burundi is facing its deepest crisis since the end of an ethnically-fuelled civil war in 2005. The unrest was triggered by the President's decision to seek another five years in office.
The presidential election is due to be held on June 26th. Parliamentary and local council polls will now be held on June 5th, delayed by a little more than week.
Burundi police fired teargas at protesters who have demanded that President Pierre Nkurunziza end his bid for a third term, in a resurgence of unrest that has stoked fears of ethnic conflict in Africa's Great Lakes.
Reuters said at least eight of the flag-waving and chanting demonstrators were dragged off by police. Some in the crowd responded by pelting officers with stones and rocks.
Separately, shots were fired at the offices of the European Union's representative in Bujumbura, prompting the mission to demand the government step up its security. The EU gave no more details.
EU officials have confirmed that shots were fired at the offices of the European Union's representative in Burundi. The union has demanded that the east African nation's government provide tighter security to the mission.
Burundi's President Pierre Nkurunziza has made his first public appearance since an attempted coup last week failed to oust him and warned of the threat posed by Islamist militants from Somalia.
At a media conference Mr Nkurunziza did not directly address the crisis in his country, which started when he said planned to seek a third term in office, but said he was "very preoccupied" by the threat posed by the al-Qaeda linked militant group al Shabaab.
Burundi contributes forces to an African Union peacekeeping mission which has been battling al Shabaab in Somalia. In recent years, the group has attacked Kenya and Uganda, which also provide troops.
Meanwhile, a leader of a group of Burundian civil society groups, Vital Nshimirimana, said demonstrations against Mr Nkurunziza's proposed third term bid would resume on Monday.
In a statement he said: "We ask the international community to follow closely the situation in Burundi in order to stop the harsh reprisal against protesters, civil society activists and opposition leaders."
Burundi's president Pierre Nkurunziza has said his country is at peace and all borders are open, in a radio address to the nation.
It follows a failed attempt to overthrow him by the army general who has since been arrested, along with a number of others who helped him.
Mr Nkurunziza said "there is peace in the whole country, including in the capital city where the coup-makers were operating".
He added that those who want to use violence "will never succeed" and called for an "immediate stop to protests" and dialogue to resolve disagreements.
Protesters opposed to the president's decision to stand for a third term have pledged to go back to the streets, setting the stage for more clashes.
The army general who led an attempt to overthrow Burundi's sitting president has been arrested, along with a number of others who helped in the failed coup.
Major General Godefroid Niyombare announced he had "sacked" President Pierre Nkurunziza while he was in Tanzania on Wednesday, following weeks of violent protests.
He went on the run after government forces seized back control of capital city Bujumbura, but was arrested this afternoon.
Nkurunziza has also returned to Bujumbura, and said those arrested would be answerable to the judiciary for their actions.
Meanwhile, 12 soldiers who had backed the coup were killed yesterday when they tried to force their way into the state radio station's headquarters, sparking a fierce gun battle and forcing the station off the airwaves for a short while.
Army Chief of Staff General Prime Niyongabo revealed 35 other "mutineers" were injured, and 40 surrendered.
The US Embassy in Burundi has closed and all non-emergency personnel, including the dependents of government staff, are leaving the country, the embassy has said.
It has not yet been decided whether the embassy will reopen on Monday.
It comes after weeks of violent protests over the president's decision to stand for a third term.
A police general and two army generals have been arrested in Burundi for their part in a failed coup to overthrow the country's president.
While the leader of the coup, Major General Godefroid Niyombare, remains on the run, government forces have gained control of capital city Bujumbura back from rebels who supported the ousting of President Pierre Nkurunziza.
The attempt to seize power came after weeks of rioting and violent protests sparked by Nkurunziza's announcement that he intended to run for a third term, which many saw as violating the country's constitution limiting presidents to two terms.
His supporters, backed by the country's court, said his first term was exempt from the rule as he was chosen by law-makers, rather than voted in in an election.
But critics have questioned the court's impartiality in making that decision.
The president of Burundi has returned to the country following an attempt to overthrow him.
Pierre Nkurunziza - who sparked protests when he confirmed he would stand for another term in office - had been in Tanzania on Wednesday when the attempted coup happened.
"President Nkurunziza is back in Burundi after the attempted coup. He congratulates the army, the police and the Burundian people," the message from the presidential office said.
It follows violent clashes in the capital Bujumbura, where broadcasts on state radio had to be briefly suspended after heavy gunfire was heard at its headquarters.