One of Burundi's vice-presidents has fled the country, saying he felt threatened after opposing President Pierre Nkurunziza's third-term bid.

Burundi has seen months of turmoil since Mr Nkurunziza announced that he would be running for office again.

Gervais Rufyikiri told France24 TV that the president's bid was unconstitutional.

A government spokesman denied that Mr Rufyikiri had been threatened.

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.

Mr Rufyikiri has been sidelined from the governing CNDD-FDD party since April, when he told a party conference that he could not support Mr Nkurunziza's re-election.

The vice-president is the latest in a series of high-profile Burundians to leave the country, including a constitutional court judge and a member of the electoral commission.

Mr Nkurunziza's critics say that a third term contravenes the constitution, which requires the president to step down after two terms.

But Burundi's Constitutional Court ruled that his 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.

The United Nations is currently trying to broker talks between the governing party and the opposition to resolve tensions.