A 17-year-old boy is amongst five people who have been arrested on suspicion of being part of banned right-wing group National Action.
He has been detained, along with three men and a woman, by West Midlands Police.
A spokesperson for the force said: “A 22-year-old man from Birmingham, a 23-year-old man from Halifax, a 22-year-old woman also from Halifax, a 28-year-old man from Birmingham and a 17-year-old boy from Nottingham will be questioned on suspicion of being members of a proscribed organisation (National Action) contrary to section 11 of the Terrorism Act.”
This is classified as a terrorism offence.
All five are being held at a police station in the West Midlands.
Multiple properties are being searched in connection with the arrests.
The capture of the suspects was “pre-planned and intelligence-led”.
A ban on membership of National Action came into force in December 2016.
This was introduced by the government and made being part of the group a criminal offence.
This can carry a sentence of up to 10 years' imprisonment.
At the time the ban was brought in, the Home Office said the group was the first far-right organisation to be proscribed as a terrorist organisation.
