The Nigerian militant group Boko Haram has announced it is joining Isis (Islamic State) by apparently releasing an audio statement swearing allegiance to the movement's leader.
The declaration means Isis can now add swathes of northern Nigeria to a self-declared caliphate that already stretches across Syria and Iraq.
This year analysts noted the growing sophistication of videos released by the Nigerian group, suggesting the two jihadist networks were growing closer.
In an audio message posted on the group's Twitter account, it said: "We swear our allegiance to to the Caliph of the Muslims [Abu Bakr al-Baghdadi], and all hear and obey him in times of difficulty and prosperity, in hardship and in ease, and to endure being discriminated against ..."
The declaration of allegiance is the latest by a series of violent jihadist groups, including several in Libya.
But Boko Haram's 51,800sq km of territory, from where it is able to launch attacks with ease, makes it one of the most important factions now flying the black Isis flag.
The message, apparently delivered by Boko Haram's leader Abubakar Shekau, goes on to call for the world's Muslims to unite. "We call on all Muslims everywhere to pledge allegiance to the Caliph and support him ..." said the message in Arabic.
Boko Haram - which means "Western education is a sin" - has been fighting to build an Islamic state in northern Nigeria for the past six years.
Last April it sparked worldwide revulsion when its fighters kidnapped more than 270 schoolgirls in Chibok.
In recent months it has forced girls as young as 10 to walk into markets with bombs hidden beneath their clothes before detonating them by remote control.
The announcement came as Boko Haram is apparently beaten out of captured territory by the Nigerian army and its allies, returning it to its previous campaign of urban guerilla warfare.
Yesterday, four bomb blasts killed at least 50 people in the northeastern Nigerian city of Maiduguri.
The attack was claimed by Al-Murabitoun, Arabic for "The Sentinels", an al-Qaeda splinter group led by Mokhtar Belmokhtar, who became internationally notorious for masterminding the massacre of 40 hostages at a gas plant in Algeria in 2013.
Algerian-born Belmokhtar, who has a 3.3 million ($7.74 million) bounty on his head, is nicknamed "Mr Marlboro" because he funded terrorism through the illegal trade in tobacco.
In other developments yesterday:
A Canadian special forces soldier was killed and three others wounded in a friendly fire incident in northern Iraq, Canada's Defence Department said. Canadian troops training local forces had just returned to an observation post at the front line when they were mistakenly fired upon by Kurdish fighters, the military said. Australian Prime Minister Tony Abbott has a message for anyone thinking of travelling overseas to fight in the Middle East: "If you get out and try to come back we'll stop you at the border on the way back," he said. Two brothers, aged 16 and 17, were intercepted at Sydney airport on Friday night after a luggage search raised suspicions they intended to join the conflict in the Middle East.
More than 300 dangerous jihadists have returned to Britain after fighting with Isis - far more than previously thought, the Sunday Telegraph reported. About 700 Islamists considered "dangerous" by the intelligence services have travelled to Syria and Iraq since the start of a conflict that has seen huge swathes of the region over-run by jihadists. Of those, about 320 have now returned and are officially listed as "people of interest".
A further 700 people - mainly British Muslims - who are not considered to be a threat to national security have also visited the region. Previously the Government had estimated 500 jihadists had fought with Isis and 250 had come back.
Fears for Libyan heritage sites
The Libyan capital of Tripoli lies more than 2735km from the ancient Iraqi city of Nimrud.
But for Mustafa Turjman, head of archaeological research at the University of Tripoli, the reported destruction of Nimrud's ruins last week by the bulldozers of Isis must have seemed rather closer to home.
Yesterday the militants looted and damaged the ancient city of Hatra. Residents heard two large explosions, then reported seeing bulldozers begin demolishing the site.
Libya, like Iraq, is home to a prized array of temples, tombs, mosques and churches, including five Unesco world heritage sites. And Libya, like Iraq, is racked by a complex civil war in which Isis plays a key role.
By the Mediterranean sprawls what remains of the town of Leptis Magna, one of the world's most impressive relics of Roman history. Up the coast to the west is Sabratha, another Roman site famed for its vast amphitheatre. And along the shoreline to the far east sits Cyrene, one of the oldest colonies of the ancient Greek empire.
Further south is Ghadames, one of the most ancient settlements in north Africa. And in the deepest south, the Acacus mountains host generations of prehistoric rock paintings.
Isis affiliates in Libya have not yet targeted any of these sites, but the group dominates two towns on the shoreline - Derna and Sirte - and has a presence in others. So there are fears for the museums and non-Islamic sites within its reach.
- Observer, Telegraph Group Ltd, AP, AAP