The runner-up in Nigeria's presidential poll, Gen Muhammadu Buhari, has said there were widespread irregularities in Saturday's election.

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.

Analysis
Muhammad Jameel Yushau

BBC Hausa Service

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Both the winner of Nigeria's election, Goodluck 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. Often they are only remembered by politicians at elections, when they are sometimes paid to do their bidding. They could further any conflict beyond control, because it provides them with an opportunity to loot and attack the people they perceive as their enemies.

Irrespective of political party and region, 12 years of civilian rule has brought little change to the lives the Nigerians. But the north is far behind the south in terms of development, education and the availability of economic opportunities. Good governance not political platitudes from the elite is what many say is needed for the future.