People from the Caucasus "are often recruited in affluent European countries by representatives of the Salafi community, " Mr. Magomedov said.

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The rise of the Muslim Brotherhood and of the more radical Salafi Islamist groups has unsettled many Christians in Egypt.

BBC: Worry taints Egyptian Coptic Christmas

In February, a leftist politician, Chokri Belaid, was assassinated and the men eventually arrested were described as being linked to salafi groups.

NPR: Jihadi Peril Makes Its Way To Tunisia