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.
The arrests come as Europe is on high alert following the terror attacks in Paris which have left 129 dead and hundreds injured.
The arrests come after an ISIS terrorist bragged about how easy it was to smuggle thousands of covert jihadists into Europe under the guise of being a desperate refugee.
The Syrian operative claimed more than 4,000 covert ISIS gunmen had made it into western nations, hidden among innocent refugees.
He said members of the blood-thirsty group were following the well-trodden route taken by refugees and migrants fleeing Syria, travelling across the border of Turkey then on to boats across to Greece and through Europe.
The man claimed there are now more than 4,000 covert ISIS gunmen “ready” to strike across the European Union.
He said it was the beginning of a larger plot to carry out revenge attacks in the West in retaliation for the US-led coalition airstrikes.
He said extremists are taking advantage of developed nations’ generosity towards refugees to infiltrate Europe, he said.
More than 1.5 million refugees have fled into Turkey alone – desperate to escape the bloodshed in Syria.
From Turkish port cities like Izmir and Mersin, thousands of refugees venture across the Mediterranean aiming for Italy, he said.
Then the majority make for more welcoming nations like Sweden and Germany, turning themselves over to authorities and appealing for asylum.
He said: “They are going like refugees.
“It’s our dream that there should be a caliphate not only in Syria but in all the world.”
Two Turkish refugee-smugglers backed up the claims made by the terrorist.
One admitted to helping more than ten trained ISIS rebels infiltrate Europe under the guise of asylum seekers.
He said: “I’m sending some fighters who want to go and visit their families.
“Others just go to Europe to be ready.”
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