Boko Haram has pledged allegiance to the Islamic State group after three bombs wreaked havoc in northeast Nigeria, killing 58 and wounding scores.
"We announce our allegiance to the Caliph of the Muslims, Ibrahim ibn Awad ibn Ibrahim al-Husseini al-Qurashi," said a voice - believed to be that of Abubakar Shekau - in an audio recording released on Twitter.
Qurashi is better known as Abu Bakr al-Baghdadi, leader of the IS group that has proclaimed a caliphate in parts of Syria and Iraq.
The eight-minute speech, in which Shekau was not shown, was published on a Twitter account used by Boko Haram and subtitled in English, French and Arabic.
The Nigerian militants' six-year insurgency has claimed more than 13,000 lives and left 1.5 million people homeless. In recent weeks, their videos have increasingly resembled IS group propaganda.
The announcement came as Boko Haram is apparently pummelled out of captured territory by the Nigerian army and its allies, returning it to its previous campaign of urban guerilla warfare.
On Saturday, a woman with explosives strapped to her body blew herself up at Baga fish market in the Borno state capital, Maiduguri.
About an hour later, another blast rocked the popular Monday Market, causing chaos as locals voiced anger at security forces who struggled to control the scene.
Just after 1pm, a third blast hit a used car lot attached to the busy Borno Express bus terminal.
There were indications that the second and third blasts were also carried out by suicide bombers but details were not immediately clear.
Borno's police commissioner Clement Adoda gave a toll of 58 dead "for the three locations" in Maiduguri and 139 wounded.
Danlami Ajaokuta, a vigilante leader whose fighters have been working with military across the northeast, said the fear of further attacks had prompted the closure of all businesses in Maiduguri.
Borno state's Justice Commissioner Kaka Shehu blamed Boko Haram and described it as a response to the defeats suffered by the insurgents in recent weeks.
"The terrorists are angry with the way they were sacked from towns and villages and are now venting their anger," he said.
