Former Costa Rican President and Nobel Peace laureate Oscar Arias says it is too early to claim victory in Sunday's presidential election.

With 75 percent of ballots counted, the center-right Arias maintains a slender lead over his nearest rival, center-left candidate Otton Solis. Arias has won just over 40 percent of the vote, while Solis has exactly 40 percent.

A candidate needs to finish ahead and win at least 40 percent of the vote to avoid a runoff.

Solis's running mate, Epsy Campbell, says her party will seek a complete recount if Arias is declared the winner.

Turnout for Sunday's election was the lowest in Costa Rican history. Observers say voters are disillusioned after a string of recent scandals involving three ex-presidents.

Some information for this report was provided by AFP, AP and Reuters.