Voters in Guinea Bissau are heading to the polls Sunday to choose a new president.

The tiny west African nation has struggled through a dictatorship, three coups and the 2009 assassination of a president since gaining independence from Portugal in 1974. No president has served a full five-year term.

A challenge facing the nine candidates seeking the presidency is overcoming the use of the islands as a shipping point for the cocaine trade.

Among the front-runners is former president Kumba Yala, who was overthrown in a 2003 coup. Another top candidate to become president of Guinea Bissau is Carlos Gomes Junior of the ruling African Party for the Independence of Guinea and Cape Verde. He resigned as prime minister to run for president.

If no candidate wins a majority Sunday, a runoff will take place next month.

The winner will succeed Guinea Bissau's late president Malam Bacai Sanha, who died in January following a lengthy illness.

Dozens of international observers will be monitoring Sunday's vote.