- The two teenagers were arrested on Sunday in Kenya
- They are being questioned by British police
- The men, who have not been named, are from Cardiff in Wales
Two 18-year-old men were detained Wednesday under anti-terrorism legislation as they arrived in Britain from Kenya, where they were initially arrested, London's Metropolitan Police said.
The men, both from Cardiff in Wales, were held under a provision of the Terrorism Act 2000 on their arrival at London's Heathrow Airport on Wednesday afternoon, a police statement said.
Under the legislation, they can be questioned for up to nine hours to determine whether they have been involved in any terror-related offenses.
The Metropolitan Police and South Wales Police declined to name the men or give more details when contacted by CNN.
Kenyan police had arrested the pair this week and put them on the plane for Britain.
A Home Office spokesman said: "We are aware of the arrests of two British nationals in Kenya on October 16. Consular assistance has been provided."