Police again used tear gas and water cannons to disperse hundreds of protesters in Bujumbura on Monday.
Youths, including students, milled about in several neighbourhoods, including Bujumbura rurale, an opposition bastion on the outskirts of the Burundian capital.
Nkurunziza, who came to power10 years ago after a bloody civil war (1993-2006), is facing a grassroots movement opposed to his candicacy, endorsed by 93 per cent of delegates convention of the ruling Conseil national pour la défense de la démocratie/Forces de défense de la démocratie (CNDD-FDD) at the weekend.
Anti-Nkurunziza activists straddle Burundi’s Hutu-Tutsi ethnic divide and include the country’s influential Catholic Church and even dissidents from CNDD-FDD ranks.
"There’s been a lot of voices from different parties, from different ethnic backgrounds who have been opposed to the third mandate," said blogger Karl-Chris Nsabibyumva in a phone interview from Bujumbura.
Rights activists say at least five people were killed on Sunday in two separate incidents – three at the hands of the police and two in clashes with the youth wing of the ruling CNDD-FDD.
"The police, they are using real bullets," one protester said Sunday in a phone interview, requesting that his name not be used.
Authorities have denied that police shot protesters. Speaking Monday on national public radio, Bujumbura Mayor Saïdi Juma blamed the deaths on "demonstrators".
Willy Nyamitwe, a presidential media advisor, went further, writing on his Facebook page that "several of our fellow citizens have been bumped off and/or burnt alive by young insurgents […] in neighbourhoods that are today spearheading the insurrection."
The authorities’ claims are likely to be dismissed by many, according to Orion Donovan-Smith, a Bujumbura resident and conflict resolution specialist.
"A majority of residents in Bujumbura support the opposition and are generally sceptical about government claims," he said in a phone interview.
It’s unclear, however, if the anti-Nkurunziza sentiment is as strong outside the capital, where only about 10 per cent of Burundi’s 10-million-strong population lives.
More than 200 people have been arrested, according to Mayor Juma. Those detained include rights activist Mbonimpa, the leader of Burundi's human rights association, Aprodh, who was detained Monday.
Independent radio station RPA that had been broadcasting details of the protests live has been shut down.
Powerful Interior Minister Edouard Nduwimana has blamed media for stirring up anti-government sentiment at a time when all demonstrations have been banned.
"There is a risk that protests called by some politicians and members of civil society may turn into clashes," Nduwimana told journalists on Sunday. "That risk is mainly the media’s fault, especially the RPA, which is broadasting this kind of event live."
His opponents say Nkurunziza’s bid for another term violates the constitution, which sets a two-term cap on the five-year presidential mandates. Supporters say his first term does not count because he was designated by unelected lawmakers, not voters.
"There is a little bit of unclarity there," acknowledged Ghent University researcher Tomas van Acker. "Nkurunziza and his supporters say: Actually this is not the third mandate, this is the second mandate [so] legally this is a perfectly legitimate candidacy."
The protesters’ ultimate goal seems unclear, according to some observers.
"Even the leaders of the movement aren’t clear whether people should go on the streets to ask for the president to say that he won’t run again or to ask him to basically just quit," noted blogger Nsabibyumva.
One protester who asked that her name be withheld expressed her disappointment at the president’s determination to hang on to power.
"The Burundian people want peace," she commented. "Burundian people want development. They are united right now to say no to that violation of [the constitution]."
Follow Michel Arseneault on Twitter @miko75011