Bujumbura--More than 22 people have been killed and scores wounded since late April, when Burundi's ruling CNDD-FDD party -- which has been accused of intimidating the opposition and arming its own militia -- nominated Nkurunziza to stand for re-election in June 26 polls.
More than 50,000 Burundians have fled the violence to neighbouring nations in recent weeks, with the UN preparing for thousands more refugees.
There was uncertainty over the whereabouts Nkurunziza, whose attempt to return home from Tanzania after the coup was announced was blocked by his opponents who seized the airport and ordered the borders to be shut.
An AFP correspondent confirmed the airport in the Burundian capital had been shut and appeared to be in the hands of pro-coup forces.
Reports suggested Nkurunziza had returned to Tanzania after his plane had been forced to turn back.
The attempted coup has sparked international alarm, with Washington urging Burundians to "lay down arms, end the violence and show restraint".
Those calls were echoed by the European Union which warned it was "essential the situation does not spin out of control".
UN Secretary General Ban Ki-moon also made an urgent appeal for calm, while the Security Council said it would hold an emergency meeting on the situation on Thursday.
In his message announcing the coup, Niyombare signalled he did not want to take power himself, vowing to form a "committee for the restoration of national harmony" and work for "the resumption of the electoral process in a peaceful and fair environment."
Niyombare is a highly respected figure who was sacked from his intelligence post in February after he opposed Nkurunziza's attempt to prolong his 10-year rule.
Asked to rule on the issue of a third term, Burundi's constitutional court found in the president's favour but not before one of the judges fled the country, claiming its members were subject to death threats.
AFP
