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

The pledge to IS, also known as ISIS and ISIL, came in an Arabic audio message with English subtitles alleged to have come from Boko Haram leader Abubakar Shekau and posted Saturday on Twitter, according to the SITE Intelligence monitoring service. "We announce our allegiance to the Caliph of the Muslims," said the message. IS leader Abu Bakr al-Baghdadi has declared himself the caliph. Earlier, Boko Haram was blamed for four suicide bombings that police said killed at least 54 people and wounded 143 in Maiduguri, the capital of Borno state and birthplace of Boko Haram. - AP