Nigeria's Boko Haram pledges allegiance to Islamic State

In 2009 Boko Haram began a campaign to impose Islamic rule in northern Nigeria. Credit: Reuters/Bate Felix Tabi Tab

Nigeria's militant Islamist group Boko Haram has pledged allegiance to Islamic State, which rules a self-declared caliphate in parts of Iraq and Syria, according to an audio statement.

In a message believed to be from leader Abubakar Shekau the group said: "We announce our allegiance to the Caliph ... and will hear and obey in times of difficulty and prosperity".

Boko Haram has been waging a six-year military campaign to carve out an Islamic state in northern Nigeria.

Today four bomb blasts killed at least 50 people in the north eastern Nigerian city of Maiduguri in the worst attacks there since Boko Haram militants tried to seize the town in two major assaults earlier this year.