Initial reports indicate the voting has gone well in Nigeria's presidential poll, in contrast to a number of previous contests marred by violence and fraud.
Observers said voters turned out in large numbers Saturday to elect incumbent President Goodluck Jonathan to his first full term or one of two main challengers. Mr. Jonathan assumed the presidency last year following the death of his predecessor, President Umaru Yar'Adua.
Security was tight at polling stations across the West African nation, Africa's most populous state. And despite two explosions in the northeastern city Maiduguri early Saturday, observers said voting had mostly proceeded calmly and with few instances of cheating.
Counting was already underway Saturday evening in some precincts.
Mr. Jonathan told voters his country was experiencing a "new dawn" of political expression as he cast his ballot. He pledged the vote would be free and fair and said he would not interfere with the outcome.
He is the clear frontrunner in the race and has promised to improve the economy, health and education in the oil-rich country.
He faces two main challengers who failed to form an alliance in a last-minute bid to force a run-off.
Jonathan's top rival is former military ruler Muhammadu Buhari, who has run for president and lost twice before. As Buhari voted Saturday, he said he would not contest the results of this election, should he lose.
Nuhu Ribadu, a former anti-corruption chief, also is considered a contender for a possible second-round election.
Buhari has vowed to clean up corruption and invest in Nigeria's infrastructure, while Ribadu has said his top priority is lifting ordinary Nigerians from poverty.
Authorities have closed the borders during the vote.
Election officials say Nigeria was prepared for the presidential poll, after delays earlier this month due to logistical problems and a shortage of printed ballots for parliamentary races.
Partial results of last week's parliament vote indicate Mr. Jonathan's ruling People's Democratic Party (PDP) lost some ground, but will retain its majority. Parliamentary voting went forward Saturday in election districts where voting could not take place last week, making up about 15 percent of all polling places.
International monitors described the conduct of last Saturday's election as "encouraging," in contrast to 2007 vote, which the European Union declared "not credible."
Nigeria is scheduled to hold state level elections on April 26.
Some information for this report was provided by AP, AFP and Reuters.