Burundi's President Pierre Nkurunziza has rejected EU and US calls to delay controversial elections set for June.

He told the BBC that such a move would plunge Burundi into a deeper crisis.

At least 18 people have been killed in protests against his bid for a third term and more than 50,000 have fled to neighbouring states.

Belgium said it was suspending nearly $6m (£3.8m) in aid to Burundi, as the EU and US warned that credible elections could not be held by June.

Last week, African Union (AU) commission chief Nkosazana Dlamini-Zuma also said the climate in Burundi was not conducive for elections.

Appeal for calm

Mr Nkurunziza told the BBC's Emmanuel Igunza that the protests against his third-term bid had been orchestrated by "outside forces" and the deaths were regrettable.

Burundi's opposition and civil society groups insist that Mr Nkurunziza's third-term bid is unconstitutional and he should step down.

But the president argues his first term does not count as he was appointed by parliament, not directly elected by the people. Last week, the constitutional court backed this interpretation.

Mr Nkurunziza, a former rebel leader, has ruled Burundi for nearly 10 years.

Protests against Mr Nkurunziza continued in parts of the capital, Bujumbura, on Monday.

The protests have taken place almost daily since Mr Nkurunziza announced his re-election bid on 25 April.

"We encourage the government of Burundi to take measures to calm the situation, and the idea of a delay in the electoral timetable would be for us a good thing," EU special envoy Koen Vervaeke said at a press conference in Bujumbura.

US ambassador Dawn Liberi read a similar statement, AFP reports.

Belgium, Burundi's former colonial power, said it would withhold about $2.2m it had pledged to help organise the elections.

It also said that it would pull out of a $3.5m police cooperation deal with Burundi.

Burundi's police have repeatedly been accused of using violence to end the protests.

The US has warned that Mr Nkurunzziza's re-election bid violates a peace accord which officially ended a 12-year civil war in the poor central African state.

Some 300,000 people were killed in the conflict.