President Muhammadu Buhari has taken an early lead as votes are being counted in Nigeria's general election, amid allegations of manipulation.
Mr Buhari has won seven of Nigeria's 36 states, while his rival Atiku Abubakar took two states and the capital Abuja.
As results came in, Mr Abubakar's People's Democratic Party (PDP) alleged that there had been irregularities in the vote.
Party chair Uche Secondus called the count "incorrect and unacceptable".
He said there had been an "attempt by the government and other agencies to manipulate the result", but did not give any evidence.
The EU, US and African Union have all expressed concern about delays and logistical problems with voting on Saturday, but no independent observers have suggested fraud.
Final results are not expected until later in the week. But Mr Secondus has criticised the initial tallies, saying the government was using "impeachments, manipulation, incarceration" to influence the outcome.
Two people were arrested in Lagos after a group of armed young men attacked voters, eyewitness Ralph Onodike told the BBC.
"What they were saying was that if you were not [voting for the ruling party] APC, you'll be attacked," he said.
In turn, the federal government accused the PDP of trying to "scuttle the polls" and prompt a constitutional crisis.
The initial vote was postponed early on Saturday 16 February, five hours before polls were due to open. Voters were also choosing members of the House of Representatives and Senate.
Most of the country was calm but there were reports of attacks by the Boko Haram Islamist militant group in the north, and voter intimidation and attempts to steal ballot boxes, especially in the southern states of Rivers, Lagos, and Anambra.
A coalition of civil society groups reported that a total of 16 people were killed around the country – fewer than in previous elections.
BBC
