Key facts about Nigeria's presidential election

Polling stations across Nigeria opened on Saturday amid tight security, as more than 56 million eligible voters went there to cast their ballots to elect a new president.

Voting in the presidential and national congress elections continued amid tight security on Sunday, as polling centers opened early to verify identities of electorates in problem areas identified by the Independent National Electoral Commission (INEC), the country's electoral body.

The following are facts of the election:

- Fourteen political parties competed in the presidential election. But it is a tight race between two parties, the ruling People's Democratic Party and the opposition All Progressives Congress.

- Only one female candidate, named Remi Sonaiya, is contesting in the presidential election. The candidate is contesting on the platform of KOWA Party.

- So far, the election has been too close to call between incumbent president Goodluck Jonathan, from the ruling party, and opposition candidate Muhammadu Buhari, who is a former military leader.

- The election is the toughest in the West African country since it reverted to democracy in 1999.

- For the first time, there is a possibility that a challenger can defeat a sitting president in the high-stakes contest to govern the country.

- Nearly 60 million people have the permanent voter cards to vote.

- Voters are also electing 360 legislators to the House of Assembly, where the opposition currently has a slight edge over Jonathan's party.

- Hackers allegedly broke into the election commission's website while voting was in progress on Saturday.

- The two main presidential candidates in the election signed a second peace accord on Thursday, to prevent violence by their supporters during and after the polls. They also pledged to accept election results as announced by the electoral body.

- The final result will be released by the electoral body, INEC, latest by Monday. Endi