What is behind religious tensions in Nigeria?

Religious tensions have risen in northern Nigeria with several bomb attacks in recent months.

They were carried out by radical Islamic called Boko Haram, which translates roughly into English as "Western education is forbidden".

Among the activities they claim to have carried out are the bombing of the UN building in Abuja, and an attack on a Christian church on Christmas Day.

Mark Doyle reports on what is behind the tension.