A blast ripped through a car park outside a stadium where Nigeria's President Goodluck Jonathan had addressed a re-election campaign rally on Monday, minutes after he left, witnesses said.
Mohammed Bolari, who was at the rally in the northeastern city of Gombe, said the explosion happened at 3:10 pm (1410 GMT), just three minutes after Jonathan's departure.
A local reporter added: "The president had just passed the parking lot and we were trailing behind his convoy when the explosion happened... just 100 metres (yards) from the bus we were driving in."