BOKO Haram, the militant Nigerian group, has announced it is allying with the Islamic State (Isis).
The pledge was made in a film, appearing to be a recording of the group's leader Abubakar Shjeka, which was posted online on Saturday evening.
Monitoring news website SITE quoted the recording as saying: "We announce our allegiance to the Caliph… and will hear and obey in times of difficulty and prosperity."
Isis has already received pledges of allegiances from militants in North Africa countries such as Egypt and Algeria, and in Libya where 21 Coptic Christians were beheaded in a coastal location in February.
Boko Haram, however, is one of the most organised groups to join forces, after running a bloody campaign for territory in the North African country since 2009.
More than 12,000 are believed to have died, some in ruthless massacre attacks. Over 1.5 million more have been made homeless fleeing the group.
Earlier on Saturday, at least 50 people were killed in suicide bomb attacks as Boko Haram's fighters attempted to seize Maiduguri, a city in north eastern Nigeria.
There were signs of the groups sharing influences in Boko Haram's most recent video, in which grainy footage of past films had been replaced by a more slick production.
The nature of the video was familiar too: two men were shown beheaded after being accused of spying.
Boko Haram came to prominence on a worldwide scaled when it kidnapped 275 girls from a school in Borno State last April - leading to the 'Bring Back Our Girls' campaign.
The group wants Islamic rule to be established in the country. Elections in Nigeria have been postponed for six weeks. Boko Haram has also moved over the country's borders and attacked in Chad and the Cameroon.
Osita Chidoka, a close associate of Nigerian President Goodluck Jonathan, warned: "The danger is that Boko Haram will try to copy groups like Isis and al-Shabaab."
"It can target the West like these groups do, target Europe, Britain - it would want to be like these other groups. The danger is that they can go beyond the region and become international.
"That is why Nigeria must be supported in what we are trying to do. We need full commitment from the international community."
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