(http://news.bbcimg.co.uk/media/images/81480000/png/_81480820_nigeria_maiduguri_neighbours_464.png) A convoy of more than 200 vehicles has been seen heading from Niger into Nigeria, while air strikes have also been reported.
On Friday, the African Union endorsed the creation of a regional force of more than 8,000 troops to combat the group.
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Colonel Sami Usman Kukasheka: "The military will definitely see to the end of the insurgency in Nigeria"
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Boko Haram at a glanceFounded in 2002, initially focused on opposing Western-style education - Boko Haram means "Western education is forbidden" in the Hausa language
- Launched military operations in 2009 to create Islamic state
- Thousands killed, mostly in north-eastern Nigeria - has also attacked police and UN headquarters in capital, Abuja
- Abducted hundreds, including at least 200 schoolgirls
- Controls several north-eastern towns
- Launched attacks on neighbouring states
Boko Haram pledge to IS raises stakes (http://www.theinfostride.com/news/world-africa-31789443)
Why is Boko Haram so strong? (http://www.theinfostride.com/news/world-africa-30933860)
Can regional force beat Islamists? (http://www.bbc.co.uk/news/world-africa-31695508)
IS shaping Boko Haram media (http://www.bbc.co.uk/news/world-africa-31522469)
(http://news.bbcimg.co.uk/media/images/75306000/jpg/_75306515_line976.jpg) Nigeria postponed national elections by six weeks until 28 March in order to have more time to try to improve security in the north.
IS took control of large swathes of territory in eastern Syria and across northern and western Iraq last year.
It has forged links with other militant groups across North Africa and the Arabian Peninsula, and in January, militants in Afghanistan and Pakistan pledged their allegiance.
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Jim Muir: "This makes them look more like a global franchise"
Nigerian officials dismissed Boko Haram's announcement of links to IS as a "sign of weakness".
Source: BBC