Counter terrorism officers stopped a man at Stansted Airport on Sunday night.
He was arrested on Monday on suspicion of terrorism offences and has been taken to a London police station where he remains in custody.
The 21-year-old had returned to the UK from Istanbul, Turkey, via Stuttgart.
Detectives says the arrest was not in response to any immediate threat or risk. Detectives have carried out searches of three addresses in connection with this investigation.
More top news
A Luton woman is facing a life sentence after pleading guilty to the murder of her sister.
Doctors at the West Suffolk Hospital in Bury St Edmunds are urging people to get their flu jab before we head into the winter months.
A mostly cloudy and breezy but rather warm day across the region with outbreaks of rain and drizzle during the morning.