Burundi riot police detain a man suspected of throwing stones during clashes in the Musaga district of Bujumbura. Picture: Jerome Delay

Bujumbura - Protest-hit Burundi cut mobile access to several social networks and messaging applications, a telecoms official said Wednesday, following days of demonstrations against President Pierre Nkurunziza's bid for a third term.

Networks including Twitter, Facebook and WhatsApp - which have been used to coordinate protests - were no longer accessible via mobile telephone in the capital Bujumbura, although an official explanation for the service cut was not been given.

At least five people have died since unrest broke out at the weekend, when the ruling CNDD-FDD party designated Nkurunziza its candidate for the presidential election to be held in the central African nation on June 26.

Opposition figures and rights groups say Nkurunziza's attempt to stand for a third consecutive term goes against the constitution as well as the peace deal that ended a civil war in 2006.

The capital Bujumbura was reported to be quiet on Wednesday morning with some shops reopening, but with a heavy police deployment on the streets, although demonstrators said they were organising themselves before protesting again.

“All the roads are blocked by police... but the protests will not stop until he gives up the third term,” said Thierry, a demonstrator. “I don't think it is going to end tomorrow or even after tomorrow.”

Nkurunziza has remained defiant: on Tuesday, his communication chief insisted he will not back down on his bid for a third term, saying that was “out of the question.”

Amid international concern, UN Secretary-General Ban Ki-moon dispatched his envoy Said Djinnit to Burundi, urging “all sides to reject violence and avoid using inflammatory language or hate speech.”

Opposition figures and rights groups say Nkurunziza's attempt to stay in power goes against the constitution as well as the peace deal that ended a civil war in 2006.

Hundreds of thousands of people were killed in the 13-year conflict, which divided the country along ethnic lines, between the Hutu majority and Tutsi people.

The government has banned all protests and deployed large numbers of police and troops onto the streets since Sunday firing live ammunition, tear gas and water cannons, with hundreds of stone-throwing protesters arrested.

Some of those killed were shot at close range, while the police said at least 37 officers have been wounded.

Police chief Andre Ndayambaje appealed for people not to turn “protests into a rebellion.”

The main independent radio station has also been shut down.

The president, a former rebel leader and born-again Christian from the Hutu majority, has been in power for two terms since 2005.

His supporters say he is eligible to run again, as his first term in office was after he was elected by parliament - not directly by the people as the constitution states.

The protesters “are people who just do not want to go to elections because they are afraid,” presidential communications chief Willy Nyamitwe said, adding the ruling party had a right to present its choice of candidate “like all other parties.”

An arrest warrant has been issued for civil society activist Vital Nshimirimana - who has since gone into hiding - but security forces have released fellow activist Pierre-Claver Mbonimpa after a day of questioning.

“They had no evidence against me,” Mbonimpa, 66, told reporters late Tuesday, saying he was held only for questioning.

“I was mistreated, roughed up.”

About 25 000 Burundians have fled the country in recent weeks, according to the UN refugee agency, which has warned the numbers could rise.

Many are fleeing threats by the pro-government militia Imbonerakure, the youth wing of the ruling party.

Rights groups allege that the militia has been armed and trained over the past year in order to help Nkurunziza remain in office.