There have been calls for a reward to be issued to those providing information about Boku Haram and its leader Abubakar Shekau

A security expert has warned about the increasing threat from the Boko Haram movement, saying that members of the insurgency group were like "fighters from hell".

Dr Ona Ekhomu, president of the Association of Industrial Security and Safety Operators of Nigeria, expressed concerns about further attacks during a public statement in which he said people who provide information that leads to the arrest of the group's members should be rewarded.

"Boko Haram fighters are fighters from hell and do not mean well for us. There are foreign fighters embedded in the group, and they are bent on destroying human lives and assets," he said.

"The Federal Government should establish a 'Rewards for Justice Programme' that will provide reward money of a minimum of N5m [£17,983] for information leading to the arrest and capture of any Boko Haram fighter.

"The recent intensification of attacks by Boko Haram signify the audacity of the terrorists who feel they can overwhelm the Nigerian government and people, and take over our territory like other terror groups have done in Mali and Iraq. This al-Qaeda brand must not be allowed to flourish in Nigeria," he said.

Boko Haram opposes the westernisation of Nigeria and wishes to impose sharia law. The group has waged a campaign of terror and violence, characterised by attacks in public spaces, such as schools and hospitals, mainly in northern Nigeria where three states - Borno, Yobe and Adamawa - have been under a state of emergency since May.

The group sparked global outcry when it abducted nearly 300 schoolgirls in Chibok, Borno State, on 14 April. Some of the girls managed to escape and return to their homes, but 220 are still missing.

The insurgents carried out another mass kidnapping in June, when they abducted 91 civilians, including toddlers, in a village in northern Nigeria. Two weeks later, 63 girls managed to flee.

Violence linked to the insurgency has resulted in an estimated 10,000 deaths between 2002 and 2013.