Turkey sent eight people with links to the so-called Islamic State group to Germany and Britain on Thursday.
A terror suspect was arrested at London Heathrow airport after he arrived on a flight from Turkey.
Police said the detention on Thursday was Syria-related.
"He was arrested on suspicion of preparation of terrorist acts," London's Metropolitan Police said in a statement.
Separately, seven prisoners deported from Turkey landed in Berlin, a Reuters witness said. The group, which included two men, four women and a child, were driven away in a vehicle.
Germany's foreign ministry had said on Monday that Ankara had informed Berlin of 10 people it aimed to deport - three men, five women and two children. The ministry has said it does not know whether any were IS fighters but it confirmed their German citizenship.
German authorities were not expected to arrest them.
NATO allies of Turkey in Europe have been worried that Turkey's offensive last month into a Syrian border area could lead to Islamic State suspects and their families escaping from prisons and camps run by Kurdish forces. Ankara has dismissed the concerns.
Turkish authorities said on Monday they had begun to send so-called Islamic State (IS) detainees back to their home countries, deporting a German and an American.
A further 23 European nationals would be sent home in the coming days.
US jihadist to be repatriated
Turkey said on Thursday would deport an American suspected jihadist fighter to the United States after he was refused entry to Greece.
Greek police said on Monday Turkish police had come to the Kastanies border post and requested that a US citizen of Arab descent accompanying them be let into Greece, as he had been arrested for exceeding his maximum permitted stay in Turkey.
The man was refused entry and returned to Turkey, Greek police said. However, Turkish state media said the man had remained in a buffer zone between Turkey and Greece.
On Thursday, the Interior Ministry said the United States had agreed to take back the man, who had requested deportation to Greece prior to being denied entry, and that Turkish authorities had begun the necessary proceedings.
Turkey says it has captured 287 fighters in northeast Syria since launching a cross-border incursion on October 9 targeting the Kurdish YPG militia.
It says it has hundreds more jihadists in detention, and has accused European countries of being loath to take back citizens who travelled to join Islamist militants fighting in Middle East wars.
Turkey has said it will send some detained militants to Ireland, Denmark and France in the coming days.