CNN  — 

Turkey has begun the process of returning alleged foreign ISIS fighters to their home countries, starting with an American, a Briton and seven Germans.

Turkey’s Interior Ministry said an American who is suspected of being an ISIS fighter was being deported the US, a British suspect to London and seven Germans to Berlin.

The American was initially sent to Greece on Monday, upon his request, according to the Ministry. But Greece refused to accept him, and he was left stranded for several days in a “buffer zone” between the countries, the ministry said.

“Upon the commitment of the USA to issue a travel document, necessary procedures have been initiated to send the foreign terrorist fighter to the USA,” the ministry said.

This comes after Turkish President Recep Tayyip Erdogan met with US President Donald Trump at the White House on Wednesday, where they discussed the fight against ISIS, among other things.

In their joint press conference, Erdogan suggested that Turkey had thousands of ISIS-affiliated individuals in its custody and was in the process of sending them back to “their countries of origin.”

On Thursday evening, counter-terror police arrested a British man on suspicion of “Syria-related” terror offenses at London’s Heathrow Airport after he arrived in the UK from Turkey, the Metropolitan Police said Thursday in a statement.

Police would not confirm or clarify to CNN if the individual arrested was deported by Turkey as part of the repatriation process.

“The 26-year-old man was arrested after arriving at Heathrow airport on an inbound flight to the UK from Turkey,” the Metropolitan Police said.

“He was arrested on suspicion of preparation of terrorist acts under section 5 of the Terrorism Act 2006 … and currently remains in police custody,” the statement added.

The UK Home Office told CNN it would not comment on individual cases.

Turkey announced last week that it would begin sending ISIS militants home, something that it has long pushed for, even for those fighters stripped of their citizenship.

Ankara has repeatedly criticized European nations for refusing to take back their own nationals, with Turkish Interior Minister Suleyman Soylu saying that Turkey was not a “guest house or hotel” for ISIS members to stay in indefinitely.

Several European countries have refused to take in the captured foreign fighters, saying that those individuals were denationalized, according to a report from Turkey’s state-run news agency Anadolu.

Danish, Irish, and French nationals are also due to be deported as part of the repatriation from Turkey, state run Anadolu news agency reported.

President Trump has previously pushed for the return of foreign fighters, calling European nations a “tremendous disappointment” for their failure to bring ISIS militants home – and threatening to dump them on their doorstep.

Last month, Trump ordered US troops to withdraw from Syria, paving the way for Turkey to launch a military operation there. The operation sought to clear a border area previously held by Kurdish fighters, whom Turkey view as terrorists, but that the US had allied with in the fight against ISIS.

Since then, fears have grown among American officials that prisons holding 10,000-plus ISIS fighters, guarded by Kurdish personnel, will be compromised – amid reports of some militants escaping.

On Thursday, the US special envoy for Syria and the Global Coalition to Defeat ISIS, Jim Jeffrey, said gains against ISIS had been threatened in the wake of the Turkish operation in northern Syria.