Nigerians are turnin out en masse to vote in a presidential election that analysts say is too close to call.

Good-humored voters smiled when electoral officials arrived late at many polling stations where registration was to start at 8 a.m. Saturday, followed by voting from 1:30 p.m.

Nearly 60 million voters are registered for the first election in Nigeria's history where an opposition candidate has a realistic chance of defeating a sitting president.

President Goodluck Jonathan and former military dictator Muhammadu Buhari are front-runners among 14 candidates seeking to govern Africa's most populous nation, which is beset by a northeastern Islamic uprising.

Dozens have been killed in pre-election violence, though leading candidates signed a peace pledge. Some 1,000 people were killed in rioting after Buhari lost to Jonathan in 2011.