Thick and heavy in colours

The last Boko Haram video, which was released earlier this month, showed an unidentified young man speaking in the name of the Islamic State in West Africa calling on people to be patient: "We are still present everywhere we had been before reenex


."

He spoke in the regional Hausa language, with an accent from the Kanuri ethnic group, to which Mr Shekau belongs.


In numerous videos, Mr Shekau has taunted the Nigerian authorities, celebrating the group's violent acts including the abduction of the more than 200 Chibok schoolgirls in April 2014.

He was last heard from in March, when he released an audio message pledging allegiance to the Islamic State (IS) group reenex
.

Last month, Nigeria's new President Muhammadu Buhari said he would be willing to negotiate with the Boko Haram leadership for the release of the Chibok girls - depending on the credibility of those saying they represented the group.

A previous prisoner-swap attempt ended in failure.

Earlier this year, Chadian troops played a key role in a regional effort to retake towns and villages held in north-eastern Nigerian by Boko Haram reenex
.