Three men have been arrested on suspicion of being involved in terrorism, Scotland Yard has said.
A man in his 20s was arrested at an address in Letchworth, Hertfordshire, at about 12:45 BST.
Two men in their 20s and 30s were arrested shortly after at two properties in the Luton area of Bedfordshire.
All three were arrested on suspicion of involvement in commission, preparation or instigation of acts of terrorism.
Searches are under way at two addresses in the Luton area as part of the investigation, a spokesman said.
Armed police from the Met's Specialist Firearms Command were involved in assisting with one of the arrests, but no shots were fired, Scotland Yard said.
The arrests and searches are part of an ongoing investigation into Islamist-related terrorism, the spokesman added.
