A senior US diplomat told Burundi's President Pierre Nkurunziza on Thursday that the east African country risks boiling over if it smothers political opposition, as protests against the president entered a fifth day.
The Burundi Red Cross said 15 protesters were injured during clashes with the police on Thursday. Some suffered bullet wounds, said one activist. Late in the day a soldier was killed by unknown gunmen, who were arrested.
Witnesses said protesters in several suburbs of the capital Bujumbura spent most of the day in a standoff with police, using smouldering tyres, sticks and stones to barricade roads.
Tom Malinowski, US assistant secretary of state for democracy, human rights and labour, arrived on Wednesday to try to prevent unrest from escalating and defuse the country's biggest crisis in years, set off by Nkurunziza's decision to seek a third term in office.
Protesters say he is violating the constitution and jeopardising a peace deal that has kept ethnic tensions in check since a civil war ended in 2005. The presidency says the protests are an "insurrection."
After meeting Nkurunziza, Malinowski told reporters he had urged him to allow peaceful criticism and room for political opposition before the June 26 vote.
"I left the president with the thought that this country with its very complicated and difficult history is like a boiling pot, and that if you try to put a lid on that pot it doesn't stop boiling. It risks boiling over," Malinowski said.
The crisis is being closely watched in a region scarred by the 1994 genocide that killed more than 800,000 people in neighbouring Rwanda, which like Burundi is divided between ethnic Tutsis and Hutus.
Other African leaders are also bumping up against constitutional limits to the number of terms they can serve; the president of Burkina Faso was overthrown last year after trying to extend his 27-year rule.
Nkurunziza told Malinowski that protests against him were illegal but that the opposition would not be restricted, according to presidential spokesman Gervais Abayeho.
The president said "political space would be respected and there is no restriction whatsoever to anybody who is engaged in political competition. Everyone has a role to play," Abayeho said.
The protesters have vowed to continue rallies against Nkurunziza.
One soldier was shot dead by six unknown gunmen in a pickup truck, witnesses said. The suspects were all arrested and the army, which did not have any immediate comment, had to prevent angry protesters from grabbing the suspects.
Protesters have often cheered when the army turns up at protests, seeing them as a neutral force. While police and protesters stay at opposite ends of streets, the army regularly mingles with protesters without problems.
Samantha Power, US ambassador to the United Nations, said on Wednesday that Nkurunziza had violated the peace deal that ended the civil war by seeking a third term. Washington was deeply troubled by arrests of protesters and the shuttering of independent media, she added.
The constitution and peace accord limit the president to two terms in office, but Nkurunziza's supporters say he can run again because his first term, when he was picked by lawmakers and not elected, does not count.