Protesters opposed to Burundi President Pierre Nkurunziza launched fresh demonstrations Monday, resuming weeks of street marches after a failed coup despite warnings from the government.

Small groups gathered in several parts of the capital, Bujumbura, singing songs and blowing whistles, each time chased away by soldiers shooting in the air, then regrouping elsewhere.

But tensions also appeared within the army that, five days on since the coup attempt led by a top general which saw soldiers battling each other on the streets, have largely replaced the police to stem the protests.

One soldier shouted at protesters to "leave the streets," warning that they were not going to fire water cannon, but guns. "We are firing water, we are firing bullets," he shouted.

Before the coup attempt the army was seen by many protesters as being more neutral than the police — often standing between demonstrators and the police — and some soldiers were unhappy at the force's role.

"We are not there to shoot people," one said.

At least 20 people died in street battles with security forces before the demonstrations ended when generals launched a failed coup attempt last week.

"Let's end fear, regain our momentum," said Pacifique Nininahazwe, a leading figure of the protest against Nkurunziza's bid for a third term in power.

Nininahazwe called for a "peaceful march," "no insults" and no stones to be thrown.

"We stop when police confront us, we sit with hands in the air, then we resume walking," he said, in a message spread via social media, after four key independent radios were closed by the authorities.

In the capital's Nyakabiga district, the army fired shots into the air, with protesters reacting by lying down on the ground, raising their hands in the air and singing the national anthem.

Bujumbura mayor Juma Saidi, speaking on state television on Sunday, warned that "demonstrators will be considered as part of the coup, and security forces have been ordered to treat them as such."

A group of top generals on Wednesday launched a bid to oust Nkurunziza while he was on a visit to neighboring Tanzania after almost three weeks of protests over his controversial bid to stand again for office.

Nkurunziza has been accused of launching a campaign of repression against opponents and trying to silence independent media since coup leaders admitted defeat on Friday after fierce fighting with loyalist troops.

Seventeen alleged plotters appeared in court on Saturday, including a former defense minister and two top police commissioners, to face accusations of "attempting to overthrow the state."

Opposition and rights groups insist that Nkurunziza's bid for a third five-year term is against the constitution and the terms of the peace deal that brought an end to the country's civil war in 2006.

The president has also been accused of intimidating opponents and failing to lift the fortunes of small landlocked Burundi, one of the poorest countries on the planet.

Nkurunziza, a former rebel leader and born-again Christian who believes he has divine backing to lead the country, argues his first term did not count as he was elected by parliament, not directly by the people.

There are fears Burundi could slide into a cycle of vicious reprisals against anyone linked to the coup, after witnesses and security sources said troops loyal to the president have been hunting down rival soldiers, even the wounded in hospital.

Many are fearful of reprisals.

"We are afraid, we wait at home without knowing what will happen," said one resident, fearing attacks by the Imbonerakure, the youth wing of the ruling party.

"If they want to kill us, who will talk about that?" he added, pointing out that key independent radio stations were closed.