Four men have been arrested moments after they arrived in Luton Airport on board an international flight.
Airport police arrested the men and handed them over to anti terrorism officers from the Met Police Counter Terrorism Command.
The men, all Sri Lankan nationals, arrived in Luton on Wednesday evening.
They are currently being held in a Bedfordshire police station.
They have not been charged, so remain unidentified.
Scotland Yard confirmed the investigation is currently ongoing.