Police sources said one of the suspects had a hand-drawn picture of a planned route from Turkey to Germany, via Greece, Serbia and Hungary.

It is believed the group are Islamic State militants planning to make their way to Germany posing as refugees.

The Anadolu Agency said the group arrived in Istanbul from Casablanca, Morocco, and were interviewed by criminal profiling teams at Ataturk Airport.

Anadolu said the eight claimed to be tourists visiting Istanbul but a hotel refuted claims they had reservations there.