BBC investigation has found evidence suggesting some results from Nigeria’s presidential election may have been manipulated.
The winner Bola Tinubu is due to be inaugurated on 29 May but the opposition is challenging this.
The BBC has uncovered significant anomalies in Rivers state, a key battleground, although not sufficient to change the overall national outcome of the election, which took place in February.
There are also questions over the identity of an election official who read out some of the unexplained results.
How votes are counted in Nigeria
On 25 February, Nigerians cast their votes at thousands of polling stations across the country.
At each polling station, the votes for the party of each candidate were publicly announced and the results sheets taken for collation first at the ward level, then at local government (LGA) centres.
An election official from each LGA then travelled to the state capital, where these results were officially declared.
For the first time in a Nigerian election, photographs of the polling station results sheets were published online by the electoral commission.
This made it possible to add up all the polling station sheets and to compare them with the results declared at the state level.
What we found in Rivers state
We added up the voting tally sheets from over 6,000 polling stations in Rivers state, where many of the opposition complaints had been made.
While the official result in this state gave a clear majority to Bola Tinubu of the ruling All Progressives Congress (APC), our tally suggested that Peter Obi of the Labour Party (LP) had actually received most votes in the state by a wide margin.