Two bomb explosions at a bus station in northeastern Nigeria yesterday killed at least 20 people and wounded 40, an emergency services official said, and witnesses said many of the victims had rushed in to help those wounded in the first blast.

No group immediately claimed responsibility for the attack in the city of Gombe. Boko Haram insurgents have repeatedly set off bombs targeting civilians, especially in the northeast, where they are trying to carve out an Islamic state.

“The second blast was worse than the first one because many people rushed to the scene and were affected. Many were killed and many injured,” witness Mohammed Fawu told Reuters by phone.

Setting off twin bombs is a classic guerrilla tactic which seeks to maximise casualties.

Hours later, an explosion shook a busy market in the north Nigerian city of Bauchi yesterday, engulfing it in flames and causing an unknown numbers of casualties, a Reuters witness said. Large sections of the central market area were on fire, sending plumes of smoke into the air.