A 16-year-old boy has been arrested on suspicion of terror offences as he prepared to leave the UK, police said.
The teenager from Kent was held by counter-terrorism officers at Stansted Airport in Essex at around 4pm on Sunday as he prepared to board an international flight.
Thames Valley Police said he was arrested "on suspicion of collection of information which is likely to be useful to a person committing or preparing an act of terrorism".
The boy was arrested by officers from the Eastern Region Special Operations Unit, working with Counter Terrorism Policing South East, which is led by Thames Valley Police.
He remains in custody.
It comes almost two weeks after another teenager was arrested for unrelated alleged terror offences.
The 17-year-old boy was held in Redhill, Surrey, on July 11 and later charged with three counts of disseminating terrorist publications and one count of preparation of terrorist acts.
At the end of June another 17-year-old boy was arrested and later charged with planning a terror attack in Cardiff.
The teenager, from the Rhondda Cynon Taff area of South Wales, was charged with obtaining a knife and hammer and preparing a suicide note for an attack.
The teenager, who cannot be identified because of his age, is also charged with posting an image and comment on Instagram to encourage others to commit acts of terror.