Malab - Africa's longest-serving leader, President Teodoro Obiang Nguema, is set for re-election as the tiny nation of Equatorial Guinea goes to the polls on Sunday.Initially scheduled to be held in November, the vote was brought forward to April 24 following a presidential decree, with no reason offered for the change.Obiang, who has ruled the west African country with an iron fist for more than 36 years, faces six candidates in Sunday's vote.The main opposition parties have however boycotted a vote that the doyen of African leaders looks certain to win.In the last election in 2009, Obiang was returned to office with a sweeping 95.37% of votes.Now aged 73, he came to power in a coup in 1979 that overthrew his uncle Francisco Macias Nguema, who had ruled the country since independence from Spain in 1968.Obiang's regime has frequently come under fire by human rights groups for suppressing dissident voices, civil society and the media, as well as for widespread corruption.Equatorial Guinea has become sub-Saharan Africa's third biggest oil producer in recent years, with revenues accounting for more than 70% of national income.But the wealth has not filtered down - while per capita national income stands at over $10 000, more than half the population lives on less than two dollars a day.The incumbent is running as head of a coalition of 10 parties that includes the ruling Democratic Party of Equatorial Guinea.His adversaries in Sunday's vote are mainly newcomers and figures with very little political weight.'Fraud' The Democratic Opposition Front (FOD) coalition of dissident groups called on March 23 for a boycott of the vote, saying it would be rigged.Andres Essono Ondo, whose Convergence for Social Democracy (CPDS) group is part of the FOD, said numerous "irregularities" surrounded the poll, which he said would ensure that "President Obiang wins with a big score as a result of fraud".The CPDS, the only opposition party represented in parliament, said it "will not recognise the president elected in the poll". The opposition says it abhors the lack of an independent electoral commission as well as the regime's grip on the media.Another FOD member, Guillermo Nguema Ela, has branded the election "anti-constitutional".Obiang and his government "do not respect either the constitution or the law", Ela said in March.But as he kicked off his re-election bid, Obiang sent a chilling warning against staying away from polling stations."I am the candidate of the people. Whoever does not vote for me is rejecting peace and opting for disorder," he said at a rally in the capital Malabo."Many say that they are tired of seeing me, it's been 36 years already. True, but I've dedicated my life to this country," he said.