West Midlands Police say that five arrests have been made in total, including a 17-year-old boy from Nottingham after a series of counter-terrorism raids across the country.
A 23-year-old man and a woman, 22, both from Halifax, West Yorkshire and two men, aged 22 and 28, both from Birmingham, were all arrested on Wednesday.
The five have been detained on suspicion of being members of a proscribed organisation, National Action, which was banned in December 2016.
They are all being held at a police station in the West Midlands, after an operation carried out by West Midlands Counter Terrorism Unit in conjunction with CTP North East and East Midlands CTIU.
A number of addresses are also being searched in connection with the arrests.
A police spokesman said: "The arrests were pre-planned and intelligence-led."