(http://news.bbcimg.co.uk/media/images/75306000/jpg/_75306516_line976.jpg)
Boko Haram at a glance(http://news.bbcimg.co.uk/media/images/81086000/jpg/_81086076_shekau.jpg) Shekau has declared an "Islamic State" in northern Nigeria
- Founded in 2002
- Initially focused on opposing Western 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 - also attacked police and UN headquarters in capital, Abuja
- Some three million people affected
- Declared terrorist group by US in 2013
Is the army failing? (http://www.theinfostride.com/news/world-africa-31046809)
Who are Boko Haram? (http://www.bbc.co.uk/news/world-africa-13809501)
Profile: Boko Haram leader Abubakar Shekau (http://www.bbc.co.uk/news/world-africa-18020349)
(http://news.bbcimg.co.uk/media/images/75306000/jpg/_75306516_line976.jpg) Some of the tactics for which IS has become so notorious, including the beheading of captives, have been used by Boko Haram.
If the group was to step up such actions as a result of aligning themselves with IS, then the prospects could indeed be even more grim.
Nigeria is a country on the fault between Islam and Christianity in Africa, where clashes with religious overtones are not uncommon.
'Arc of instability' But there are factors that complicate all the predictions about what could happen now.
Many of the groups in Africa that are open to falling under jihadi extremist influence also have members who see themselves as fighting a much more local cause. It could lead to splits over ideology and strategy. It was the case when Somalia's al-Shabab linked up with al-Qaeda.
There has also been growing international concern about the risk of a joined up jihadi-led arc of instability that would need to be confronted across the northern part of the continent.
Al-Qaeda in the Land of the Islamic Maghreb (AQIM) has been entrenching itself in several countries in the Sahel on the other side of Africa. Meanwhile, nearby Sudan, South Sudan and the Central African Republic are facing security issues and many other problems.
The British government called it a potential challenge for generations to come.
Now IS is in that mix, gaining allies in Nigeria, the region's economic powerhouse and Africa's most populous country.
Propaganda is vital to the cause, whether the driving force is IS or al-Qaeda. Local politics are often another ingredient.
And civilians are always caught in the middle.
Source: BBC