Eleven men have been detained under terror laws in coordinated raids across England and Wales as part of a national investigation into the banned far-right group National Action.
The extreme right-wing group was proscribed in the UK by the home secretary in December 2016.
The swoops were carried out by officers from Counter Terrorism Policing North East and North West, the Wales Extremism and Counter Terrorism Unit, and Wiltshire police.
Officers arrested six men in the North West of England, including one who was produced for police from prison. Three men were arrested in Merseyside: a 24-year-old man from Seaforth, a 23-year-old man from Newton-le-Willows, and a 33-year-old man from Prescott.
A 31-year-old man and a 35-year-old man were arrested in Warrington, Cheshire, and a 22-year-old man from Lancashire was produced from prison for police interview.
A 28-year-old man and a 23-year-old man were held in Swansea, South Wales; a 23-year-old man was arrested in Sowerby Bridge, West Yorkshire; a 26-year-old man was arrested in Leeds; and a 30-year-old man was arrested in Wiltshire.
All of the men have been held on suspicion of being a member of a proscribed organisation. Some were also arrested on suspicion of offences including preparation of a terrorist act, and funding terrorism.
Eleven properties are being searched across a number of force areas in England and Wales as part of the investigation.
The arrests follow activity earlier this month by West Midlands Counter Terrorism Unit.
Assistant Chief Constable Russ Jackson, who is responsible for counterterrorism policing for the North West, said: “We are committed to taking positive action such as this to remove those connected to organisations, such as National Action, from our communities.
“Individuals involved in proscribed organisations who support extremist ideologies bring damaging consequences to local communities but with the help of the public and our partners, we will do everything we can do bring these people to justice.
“All information received will be dealt with in the strictest confidence and can be passed to us anonymously by calling the Anti-Terrorism Hotline on 0800 789 321”
The senior national coordinator for counterterrorism (CT) policing, Deputy Assistant Commissioner Neil Basu of the Metropolitan police, added: "CT policing is committed to tackling all forms of extremism that threatens public safety and security. Investigations relating to alleged extreme right-wing activity are pursued with the same level or resource and vigour as other ideologies, in order to bring suspected offenders before the courts.
"Today's arrests, while resulting from two separate investigations, have been coordinated by our officers across a number of forces. This maximises operational effectiveness for police and minimises disruption for the local communities."