Police in Burundi's capital have opened fire on protesters opposing the president's bid for a third term.
They used tear gas and live ammunition on hundreds of protesters in the centre of Bujumbura - the closest the protests have got to the presidency.
More than 20 people have been killed since protests against President Pierre Nkurunziza's decision to stand for re-election began on 26 April.
Rumours of a coup on Wednesday have been dismissed by the presidency.
Burundi's presidential spokesman Willy Nyamitwe told the BBC Great Lakes service that the rumours had spread over Twitter and were unfounded.
Mr Nkurunziza is currently in Tanzania for a summit with other East African heads of state, who are expected to urge him to drop his election plans.
Meanwhile, Burundi's influential Catholic Church has called for the elections in June to be postponed.
It said in a statement that it would ask Catholics on the electoral commission to step down if the government refused to yield.
Hundreds of protesters were within about a kilometre of the presidency when police opened fire, the BBC's Maud Jullien reports from the scene.
This is the first time since the beginning of the protests that police have used tear gas and live rounds on the demonstrators, she said.
Another journalist at the scene, Melanie Gouby, tweeted: "Grenades thrown, protesters have Molotov cocktails, water cannon tank keeps falling back and protesters gaining ground."
Many of the protesters were women, who moved to a petrol station in the capital from where they said they would remain until the leaders in Tanzania dissuade Mr Nkurunziza from running in the election.
They told the BBC they had deliberately chosen the petrol station as the site of their sit-in because police were unlikely to open fire near it.
Shops and businesses have closed while barricades continue to burn in the centre of the capital.
Mr Nyamitwe said security has been tightened around the national radio station in case a demonstration targeted it.
The violence of the last few weeks is the worst violence since the end of the civil war in 2005.
The 51-year-old former rebel leader argues that he is entitled to run for a third term because he was first appointed to the role by parliament in 2005.
The constitution states a president should govern only for two terms, but earlier this month a court upheld Mr Nkurunziza's interpretation.
The UN said last Friday that more than 50,000 Burundians had fled their country since April because of fears of pre-election violence.