Nigeria's militant Islamist group Boko Haram has pledged allegiance to the Islamic State group, which rules a self-declared caliphate in parts of Iraq and Syria, according to a video posted online.
"We announce our allegiance to the Caliph ... and will hear and obey in times of difficulty and prosperity," read an English language translation of the video broadcast in Arabic that purported to be from the Nigerian militant group.
The pledge of allegiance was attributed to Boko Haram leader Abubakar Shekau.
Earlier, three explosions in the north eastern Nigerian city of Maiduguri have killed 50 people and injured more than 30, according to a senior hospital official in the city.
"We've received 50 dead bodies from the blast scenes and 36 injured people. The state government has directed the treatment for the injured persons to be free," Chief Medical Officer of Borno Specialists Hospital Salisu Kwaya Bura told reporters.
A tricycle rider with a bomb tried to enter a fish market on the Baga road in the west of Maiduguri. The bomb exploded when the tricycle was prevented from going in, Mohammad Ajia, a trader in Baga market, said after fleeing the scene.
A second blast then hit an area known as the Monday market, before a car bomb exploded by a bus station near a Department of State Security office, according to a civilian member of a joint task force.
Maiduguri is the capital of Borno state, the heartland for the militant Islamist group Boko Haram, which has long coveted the city as the capital of an Islamic state they want to carve out of religiously mixed Nigeria.
Suspected Boko Haram militants tried to seize the city at the end of January, but were repelled in fighting that killed more than 100 people.
