Five people including a 17-year-old boy have been arrested on suspicion of being members of a banned far-right group.
Two men from Birmingham aged 22 and 28, a 23-year-old man and 22-year-old woman from Halifax and the teenager from Nottingham are being held by police in the West Midlands.
They are suspected of being members of National Action.
A number of properties are being searched following the arrests.
The five suspects were detained following a series of planned arrests across the country, West Midlands Police said.
National Action was founded in 2013. It was proscribed in December 2016 after it was assessed as being "concerned in terrorism".