Heavily armed Boko Haram militants attacked the northeastern Nigerian city of Gombe yesterday.

Explosions and gunfire could be heard after the fighters overwhelmed a checkpoint at the edge of the city, which has been bombed before but has never had the insurgents attempt to take it over. Witness Abdul Hassan said soldiers ran away after the checkpoint was overwhelmed. Boko Haram's struggle for an Islamic state has become the gravest security threat to Africa's biggest economy and top oil producer, killing thousands, kidnapping hundreds and increasingly threatening neighbours Cameroon, Chad and Niger - all of which are now also battling the insurgents.