Turkey has deported some 1,500 Europeans who travel with the alleged intention to join Islamic State and other militant organisations
British police have arrested six people on suspicion of terrorism after Turkish authorities stopped a group crossing the Syrian border, police said.
Four people aged between 22 and 47 were arrested at Manchester airport in north-west England early Wednesday, following on from the arrest on Tuesday of a 21-year-old man at Birmingham airport in central England and a 31-year-old man in Rochdale, near Manchester.
The investigation was launched after nine people - five adults and four children - were stopped by Turkish authorities trying to cross into Syria last month.
Turkey deported the nine Britons, including the son of a local councillor from Rochdale, on Tuesday, two weeks after arresting them for attempting to cross into Syria to join militants, Turkey's official news agency Anatolia said.
Waheed Ahmed, 22, is son of Shakil Ahmed, a councillor for the opposition Labour Party on Rochdale Borough Council in the north of the country.
Shakil Ahmed said he thought his son had been in Birmingham on a work placement when he discovered that he had been detained in Turkey.
— Syrian Updates (@syrializer) April 13, 2015
Police searched Ahmed's home earlier this month for clues as to why his son had travelled to the country.
The four children in the group have been placed in the care of a guardian.
Turkey has in recent months been repeatedly criticised by its Western allies for not doing enough to halt the flow across Turkish territory of European nationals seeking to join extremist groups such as Islamic State.
However it has made a number of arrests in recent months in an apparent bid to deflect the criticism and insists it is doing all it can to control the border.
Turkish authorities, in large part due to information shared by European secret service agencies, have deported some 1,500 European Union citizens travelling to the country with the alleged intention to join militant organisations, according to ministry of interior data from March.