Election officials say Guinea-Bissau's presidential race will enter a second round with the former prime minister in the lead.
Provisional results released Wednesday gave Carlos Gomes Jr. nearly 49 percent of the vote. He will face Kumba Yala, who took 23 percent, in a runoff. Electoral commission president Desejado Lima da Costa said the poll's date will be set later.
Yala was among a group of five of the race's nine candidates who earlier called for the poll to be annulled, claiming fraud.
Observers have said that the election proceeded smoothly and that the vote in the West African country seemed to be transparent.
Voters hoped the poll would stabilize this coup-prone nation marred by a military assassination and the recent death of the president.