Nigeria: Leaders seek poll annulment

Nigeria's supreme court has begun hearing an appeal by opposition leaders against the victory of Umaru Yar'Adua, the country's president, in last year's elections.
Atiku Abubakar and Mohammadu Buhari, two opposition candidates, have asked the court to overturn a lower court ruling that upheld Yar'Adua's victory in the April 2007 vote.