Millions of voters in Madagascar queued in long lines early on Wednesday to cast their ballots in a presidential election, as the Indian Ocean island struggles to create jobs, fight poverty and end corruption.

President Hery Rajaonarimampianina is seeking a second term in office and his two main challengers are former heads of state Marc Ravalomanana and Andry Rajoelina.

All three have crisscrossed the island in a hunt for votes and each has pledged to accelerate recovery for an economy the International Monetary Fund (IMF) forecasts will grow at more than five percent this year, its highest rate in a decade.

Civil society groups accuse the three wealthy front runners of enriching themselves in office, something each denies.

The groups said a fisheries deal the incumbent signed with Chinese firms in September is opaque and will impoverish local fishermen.

They also said Ravalomanana failed to tackle corruption during his time in office that ended in 2009, when he was forced out by protests led by Rajoelina in what international organisations like the African Union said was a coup.

Conservation groups then accused Rajoelina, the man who ousted him, of profiting from the plunder of natural resources. Praying for change

As queues started forming on Wednesday morning in the capital, Antananarivo, voter Sahondramalala Nirisoa told Reuters news agency she had arrived early because she needed to get to work.

"I hope and I pray for a change," she said. "That is why I came to vote."

According to a World Bank report, more than 80 percent of the population lives in poverty.

There are nearly 10-million registered voters in the country of 25-million people, data from the electoral commission showed.

Few analysts expect an outright winner from the 36 total who are contesting.

If the poll needs to go to a second round, it will involve only the two top candidates and take place on December 19.

Since a peaceful election in 2013, investors and donor governments re-engaged following a four-year freeze that began after Rajoelina came to power.

The events of 2009 prompted an exodus of foreign investors from a country that is one of the world's poorest despite reserves of nickel, cobalt, gold, uranium and other minerals.

The island was hit by a fresh political crisis in April sparked by a legal amendment by Rajaonarimampianina's government that would have prevented Ravalomanana from standing for office.

Rajaonarimampianina approved a new law removing that provision the following month, allowing Ravalomanana to register as a candidate.