Nigerian President Goodluck Jonathan has sacked four ministers, in the latest shake-up ahead of elections next year.

Outgoing Aviation Minister Stella Oduah, a close ally of the president, is the most high-profile sacking.

She has been embroiled in allegations of corruption, which she denies, after her ministry spent $1.5m (£1m) on two bullet-proof luxury cars.

Mr Jonathan's party is divided on whether he should seek re-election.