Burundi goes to the polls on Monday with the president defiant in his controversial bid for a third term in power, despite weeks of unrest that forced thousand to flee and prompted international calls for a delay.

On the eve of the election, top party official and parliament head Pie Ntavyohanyuma said Sunday he had joined some 127,000 other Burundians who have fled the country, denouncing President Pierre Nkurunziza's "illegal" bid to stay in power for a third term.

UN Secretary General Ban Ki-moon has heeded the calls for the elections to be delayed after the opposition said they would not take part, as Burundi faces its worst crisis since its civil war ended nine years ago.

"I would like to say to him (Nkurunziza) that the mandate he wants to have is illegal. I would like to say to him that forcing through the election is senseless," Ntavyohanyuma told the broadcaster France 24 on Sunday.

More than 70 have been killed in weeks of violence and a failed coup sparked by Nkurunziza's bid to stay in power, with a string of grenade attacks in recent days.

Several top officials -- including the deputy vice-president Gervais Rufyikiri as well as members of the election commission and constitutional court -- have also fled the poverty-stricken, landlocked country.

But the government has defied all requests for a delay, and the electoral commission said Sunday all was ready for polling day.

"Everything is ready in the country," election commission chief Pierre-Claver Ndayicariye said Sunday, saying all voting material had been delivered to over 11,000 polling stations across the country.

The African Union announced Sunday it would not act as an observer in the parliamentary polls, saying the conditions were not right for "credible elections".

"Noting that the necessary conditions are not met for the organisation of free, fair, transparent and credible elections... the AU Commission will not observe the local and parliamentary elections," commission chair Nkosazana Dlamini-Zuma said in a statement.

- 'Sham elections' -

Almost five million are registered to vote, but the opposition are boycotting the polls, claiming it is not possible to hold a fair vote.

Voting for the parliamentary and local elections begins at 06:00 am (0400 GMT) Sunday, with the presidential vote due to follow on July 15.

Commission chief Ndayicariye said he had not received any official notification confirming the opposition withdrawal from the vote.

"This is nothing new in Burundi. In Africa, boycott is another way of doing politics," he said. The opposition boycotted polls in 2010.

Nditije insisted however that the letter announcing a boycott had been handed to the commission, and it of "lying" so as to pretend the poll will be credible.

Burundi was plunged into turmoil in late April when Nkurunziza launched his drive for a third consecutive five-year term, triggering widespread protests.

Opponents say his bid for another term is unconstitutional and violates a peace accord that paved the way to end 13 years of civil war in 2006.

Civil society groups backed the boycott in a joint statement calling on voters to skip the "sham elections" and urging the international community "not to recognise the validity" of the polls.

The ruling CNDD-FDD's youth wing, the fearsome Imbonerakure whose name means "The Watchmen" or, literally, "Those Who See Far", has been accused by the UN of waging a campaign of intimidation and violence.
Source: AFP