Guinea-Bissau is headed toward a presidential run-off election after no candidate won a majority in Sunday's first-round voting.

Official provisional results released Wednesday showed former prime minister Carlos Gomes Junior barely missed an outright victory, taking just under 49 percent.

Gomes, the ruling party candidate, will now face opposition leader and former president Kumba Yala, who came in second with 23 percent.

Yala is one five candidates who on Tuesday called for the election to be annulled because of alleged fraud. The candidates said the election lacks credibility because it was rife with irregularities.

International election observers have said Sunday's poll appeared to be free and fair.

The fraud claims have raised fears that trouble is looming in the coup-prone country, where former military intelligence chief Samba Diallo was killed hours after the polls closed.

The winner of the run-off will replace the late president Malam Bacai Sanha, who died in January after a long illness.

While Mr. Sanha was hospitalized in December, a struggle within the military and an apparent coup attempt took place.

Since winning independence from Portugal in 1974, Guinea Bissau has struggled through a dictatorship, three coups and the 2009 assassination of a president.

The country has also become a transit point for cocaine smugglers.