British counter terror police have arrested four Sri Lankan nationals on suspicion of being members of a banned organisation.
The suspects were arrested after arriving at Luton Airport on Saturday and Sunday.
The Metropolitan Police said the group were stopped under the Terrorism Act 2000 and arrested under the Police and Criminal Evidence Act 1984.
The investigation is being led by the Met’s Counter Terrorism Command.
One woman and three men were arrested on suspicion of being a member of a proscribed organisation by Counter Terrorism Policing officers from Eastern Region Specialist Operation Unit (ERSOU), media reports said on Tuesday.
A 39-year-old man, a 35-year-old man and a 41-year-old man remain in custody at a south London police station. A 35-year-old woman has been bailed to a date in early November, pending further inquiries.
They were arrested on Saturday, 5 and Sunday, 6 October under section 11 of the Terrorism Act, for membership of a proscribed organisation.
All four were arrested under PACE legislation.