Eleven men have been arrested under anti-terror laws as part of a national investigation into neo-Nazi group National Action, police have said.
The arrests include six people from north-west England, two from South Wales, one from Wiltshire, and two from West Yorkshire.
National Action became the first far-right organisation to be banned in the UK last year.
Eleven properties are being searched across England and Wales.
Those arrested – aged between 22 and 35 years-old – are all suspected of membership of National Action.
Six are also being questioned about preparing acts of terrorism and five are suspected of funding terrorism.
Being a member of – or inviting support for – a proscribed organisation is a criminal offence carrying a sentence of up to 10 years in prison.
Home Secretary Amber Rudd has previously described National Action as “a racist, anti-Semitic and homophobic organisation”.
The arrests were a result of two separate investigations coordinated across a number of police forces, Neil Basu, senior national co-ordinator for counter-terrorism policing, said.
Detective Chief Superintendent Martin Snowden, head of the North East Counter Terrorism Unit, said: “Those who promote extreme right-wing views are looking to divide our communities and spread hatred.
“This will not be tolerated and those who do so must be brought to justice.”
Earlier this month, three men – including two British soldiers – were charged under anti-terror laws with being members of National Action.