One of Burundi’s vice-presidents has fled saying that he could not support the third-term bid of President Pierre Nkurunziza.
There have been months of turmoil in the country since the president announced that he would be running for office again in July’s elections.
Gervais Rufyikiri told France24 TV that a third term for the president was unconstitutional.
A government spokesman said the vice-president is on a foreign mission.
Violent protests in the capital Bujumbura followed the 25 April announcement that Mr Nkurunziza would seek re-election.
Rights groups say at least 70 people have been killed and 500 wounded as demonstrators clashed with police over the past two months.
More than 100,000 people have fled Burundi since the start of the crisis, the UN says.
The president’s critics point out that a third term contravenes the constitution, which requires the president to step down after two terms.
But Burundi’s Constitutional Court ruled that Mr Nkurunziza’s first term does not count because he was elected by parliament and not voters.
In May, the president survived a coup attempt.
The election was due in June but was put back to 15 July following pressure from regional leaders.