Abuja - Despite a climate of tension and fear, millions of Nigerians lined up in the early hours of Saturday in presidential and parliamentary elections postponed by six weeks due to Boko Haram violence.
Fourteen presidential candidates are competing for the highest office in Africa's biggest economy. But effectively, it will be a neck-and-neck race between incumbent Goodluck Jonathan, 57, and former military leader Muhammadu Buhari, 72.
Polling stations opened at 8.00 am (0700 GMT) to verify registration and search voters for weapons, but voting will only begin at 1.30 pm. The polls will close once the last person has cast his or her vote.
Throughout the day, 68.8 million eligible voters have the option of lining up at 150 000 polling stations across the country.
They will use biometric identity cards for the first time, which authorities hope will reduce the risk of fraud. Nigeria's elections have for decades been plagued by voter irregularities.
Numerous international and local observer teams will monitor the election. The European Union sent a team of eight elections analysts and 30 election monitors, while the African Union dispatched 50 observers. The EU will not deploy in the volatile north-east due to security concerns.
Roughly 360 000 police officers have been stationed across the country to prevent violence. Security measures are particularly tight after the polls, initially scheduled for February 14, were postponed by six weeks due to fear of Boko Haram attacks.
The Islamist terrorist group has killed an estimated 14 000 people since 2009.
To win, a candidate needs more than half of the national vote and at least 25 per cent of the votes in two-thirds of Nigeria's 36 states. If no candidate gets enough votes to win outright, the election will go into a second round, which is won by a simple majority.
Nigerians are known for voting along religious and geographic lines. About half of Africa's most populous nation of 178 million people are northern Muslims, while an estimated 45 per cent are southern Christians. Five per cent belong to traditional African religions.
Nigerians are also set to elect a parliament, with 739 candidates contending for 109 Senate seats, and 1 780 candidates competing for 360 seats in the National Assembly.
Jonathan's People's Democratic Party (PDP) and the All Progressives Congress (APC), a coalition of Nigeria's three largest opposition parties, led by Buhari, are expected to win the largest numbers of seats.
Preliminary results are expected on Sunday.
Sapa-dpa