Five men and a woman have been arrested on suspicion of being members of the banned neo-Nazi terror group National Action.
Police in the West Midlands made the arrests in dawn raids on Wednesday morning (3 January), with officers searching a number of properties.
The detained men include a 26-year-old from Cambridge, a 21-year-old from Banbury, Oxfordshire, a 28-year-old from Wolverhampton, a 26-year-old from Leicester and a 24-year-old from Stockport.
A 37-year-old woman from Banbury was also arrested by counter terror police.
The five men are being held in the West Midlands and the woman at a police station outside the force area.
Police said they were all arrested on suspicion of being concerned in the commission, preparation and instigation of acts of terrorism, "namely on suspicion of being a member of a proscribed organisation [National Action]".
A statement from West Midlands Police added: "The arrests were pre-planned and intelligence-led; there was no threat to the public's safety."
Several counter terrorism units were involved in the raids.
National Action became the first British right-wing organisation to be banned in the UK when it was proscribed by Home Secretary Amber Rudd in December 2016.
It meant being a member of or inviting support for the group is a criminal offence, carrying up to 10 years' imprisonment.
Dozens of alleged members of the group have been arrested since its proscription.
Later this year a separate case will see a 22-year-old man and alleged National Action member go on trial accused of plotting to murder the Labour MP Rosie Cooper with a Roman sword.
Three other alleged National Action members, including two British soldiers, are also due to appear at Birmingham Crown Court on Wednesday in another unrelated terror case.
When she banned the group, Home Secretary Rudd said: "National Action is a racist, anti-Semitic and homophobic organisation which stirs up hatred, glorifies violence and promotes a vile ideology, and I will not stand for it.
"It has absolutely no place in a Britain that works for everyone."