Boko Haram pledges loyalty to IS

Nigeria's home-grown Boko Haram group, newly weakened by a multinational force that has dislodged it from a score of northeastern towns, reportedly pledged formal allegiance to the Islamic State group.

The pledge came in an Arabic audio message with English subtitles alleged to have come from Boko Haram leader Abubakar Shekau and posted on Saturday on Twitter, according to the SITE Intelligence monitoring service.

"We announce our allegiance to the Caliph of the Muslims ... and will hear and obey in times of difficulty and prosperity, in hardship and ease, and to endure being discriminated against, and not to dispute about rule with those in power, except in case of evident infidelity regarding that which there is a proof from Allah," said the message. IS leader Abu Bakr al-Baghdadi has declared himself the caliph.

Earlier, the extremist group was blamed for four suicide bomb attacks that police said killed at least 54 people and wounded 143 in the northeast city of Maiduguri, the capital of Borno state and birthplace of Boko Haram.

In the deadliest blast, 18 people died when a suicide bomber blew himself up in a tricycle taxi at the entrance to the bustling Baga fish market, police said.

"I saw many dead bodies lying on the ground," said fish seller Idi Idrisa.