Nummer 2 i præsidentvalget i Nigeria 16. april, general Muhammadu Buhari, siger onsdag til BBC World News, at der var valgsvindel.
There were areas in the south where his supporters were not allowed to vote, the ex-military leader told US radio.
But he said his party would challenge the result legally and urged calm after riots broke out in the north when Goodluck Jonathan, a southerner, won.
The Red Cross says 48.000 people have now fled from the violence.
In Kaduna state, police sources have told the BBC some 400 people have been arrested in connection with the clashes.
Goodluck Jonathan was declared winner of Saturday’s presidential poll, with the electoral commission saying he received about 57 per cent of the vote with 22,5 million votes to General Buhari’s 12,2 million votes.
International observers have said the election was reasonably free and fair.
Both the winner of Nigeria’s election, Jonathan, and his main rival, Muhammadu Buhari, have called for calm following the post-poll riots in the north. But the tensions cannot be plastered over.
Most of those behind the rioting have been unemployed young men – uneducated and deprived.
