Islamist militant group Boko Haram has attracted global attention after claiming responsibility for the kidnap of more than 200 schoolgirls in north-eastern Nigeria.
What is Boko Haram?
Boko Haram - the rough translation of which is "western education is sin" - was founded in north-eastern Nigeria in 2002, by radical cleric Mohammed Yusuf.
The aim of the organisation is to make the country a fully Islamic state, with criminal courts governed by sharia law.
Initially the group was not known to be violent - instead opting to publicly criticise Muslims who participated in "western norms" such as voting and secular education.
Opposition turns violent
However, from 2009, Boko Haram became more active in its attempts to overthrow the government, amid increasing clashes between Muslims and Christians in the country and accusations of state-sponsored brutality.
The first major bloodshed involving the sect was seen in a series of clashes with Nigerian security forces in northern states.
Estimates suggest these clashes resulted in at least 800 deaths - including that of Yusuf, the group's leader, whose execution in police custody was televised.
Rise in attacks on civilians
Since then the group, under the new leadership of Abubakar Shekau, has been associated with increasingly frequent, high-profile attacks.
In September 2010, an attack on a prison led to hundreds of convicts escaping, including an estimated 150 Boko Haram members.
Just under two years later, the group bombed UN offices in the capital, Abuja, killing 23 people.
'58 attacks since January'
Amnesty International told ITV News that their latest estimates indicate suspected Boko Haram members have carried out at least 58 attacks between January and the end of April this year alone.
Violence against civilians has grown in the lead up to the recent abduction of teenage girls, with the group accused of brutally murdering drivers on Nigeria's highways and killing more than 70 people in a recent bomb attack on a bus station.
State of emergency
The sharp rise in civilian bloodshed has prompted an attempted crackdown by the Nigerian government - itself accused of allowing the torture and killing of thousands in custody since the violence began.
A state of emergency was declared in three north-eastern states of Adamawa, Borno and Yobe in May last year, though Amnesty says this has done nothing to reduce the violence in the region.