The Islamic State's news agency Amaq released a video online which purportedly shows ISIS fighters patrolling the street of Mosul on Monday night.

One of the fighters, his face hidden behind a mask, looks at the camera and says "America, we will defeat you in Iraq, with Allah's help. You will leave again, defeated and humiliated, with your tail between your legs."

Iraqi and Kurdish soldiers, with the backing of the US, are advancing on Mosul to take the city back from ISIS. The US has refrained from sending its own soldiers to battle ISIS on the ground.

The European Union today expressed concern for the effect the recapture of Mosul could have on the European continent. "The retaking of the IS's northern Iraq territory, Mosul, may lead to the return to Europe of violent IS fighters," the EU's security commissioner, Julian King said. 'This is a very serious threat and we must be prepared to face it.”