Terrorists, criminals and foreign fighters are flowing into Europe among migrants, the top Nato commander in Europe says.

U.S. Air Force General Philip Breedlove said the Islamic State extremist group is ‘spreading like a cancer’ within this mix, ‘taking advantage of paths of least resistance, threatening European nations and our own’.

Breedlove, in a testimony before the Senate Armed Services Committee on Tuesday, said Russia’s actions in Syria have ‘wildly exacerbated the problem’.