As police continue to interrogate the Nigerian man who attempted to blow up a US-bound plane on Christmas day, questions have been raised about the growth of terrorism in West Africa. But although radical Islamist groups have long been active in the region, experts say the planned attack was not part of a wider trend.

Umar Farouk Abdulmutallab attempted to detonate a bomb on a flight from Amsterdam to Detroit and is alleged to have told police he was sent by Al Qaeda. Security was stepped up even further when another Nigerian man travelling on the same route on Sunday was arrested after spending an hour in the toilet. He was released after it became clear he had simply been ill. Despite continuing nervousness in the aviation world, terrorism expert Professor Paul Rogers, from the University of Bradford, told Radio Netherlands Worldwide there is no proof Islamist terror groups are operating in Nigeria.
 

 
"I think the Nigerian connection was quite a surprise. There have been many tensions between broadly the northern part of the country which is primarily Muslim and the southern part, which isn't. And you've had quite a lot of radicalism but not at the level of what you might call 'international jihadism'."

 
Big Yemen
Attention has also been focused on Yemen, where the 23-year-old suspect is believed to have received training in terror tactics. The US has invested heavily in the Middle Eastern country, but Professor Rogers says its size makes it difficult to have any real effect.

 
"There are quite large areas of the country which are not under central government control, and that is quite apart from the insurgency... developing in the northern part of the country. So although there's been a lot of money going into Yemen for counter-terrorism work, it's not a country in full control of its own territory and this means there are areas which are almost free for local Islamist groups - quite loosely connected with the Al Qaeda movement -  to develop."

 
Watch-lists
US President Barack Obama has announced a review of US terrorist watch-lists, after it emerged that Mr Abdulmutallab was not on a list of 18,000 people subject to extra security at airports worldwide. Passengers flying to the US are being subjected to extra checks, and airlines are reporting delays. But former White House counter-terrorism tzar Richard Clarke says new measures need to be introduced worldwide:"

"We really have to replace our scanning devices with more modern systems."