But he says he doesn’t believe the militia is powerful enough to organize a major attack in the West.

"I don't think myself that it has the sustainable basis for carrying organized violence against western targets in Europe and in other western countries,” he added. “But nevertheless given that individuals mobilized and indoctrinated by al-Shabaab can inflict or try to inflict harm is a serious concern."

Ehteshami says the cartoons published half a decade ago will continue to stir resentment. Last month European authorities arrested five people suspected of planning an attack on the Danish newspaper that originally published the controversial images.