THREE young men have been arrested on suspicion of terrorist offences, police confirmed today.

A 17-year-old Londoner, a 21-year old from Bath and an 18-year-old from Portsmouth were arrested in a pre-planned and ongoing investigation into far-right activity.

The arrests follow a BBC investigation into the Sonnenkrieg Division, a neonazi group with 15 members in Britain.

Sonnenkrieg has been posting propaganda messages online – including one calling Prince Harry a “race traitor” – and images of a woman hanging from a noose calling on white women who date non-white men to be killed.

The group is linked to the Atomwaffen Division, a terrorist organisation in the United States that is linked to five murders.

Hundreds of messages sent over several months were uncovered on an online gaming server, where a user dubbed “Blitzy” described Sonnenkrieg as “full on Universal Order” and that an aim is to “kill all police officers,” who should be “raped to death.”

Unite Against Fascism’s Weyman Bennett said: “This group, though very small, were clearly looking to radicalise young men particularly to perform vile acts in their nazi cause.

“Like the fascist Tommy Robinson, such people seek to influence online others to carry out fascist-inspired violence.”

Thousands of protesters are expected to turn out to counter a racist so-called “Brexit Betrayal” demonstration in central London on Sunday.

A wide cross-selection of organisations are mobilising against the Robinson supporters, including trade unions and groups representing women, LGBT+ people and faith communities, regardless of their views on leaving the EU.

Writer, broadcaster and former children’s laureate Michael Rosen said: “We know that racism, fascism, anti-semitism and Islamophobia are on the move, gathering support.

“Even worse, there are people in positions of power and influence who have put in place discriminatory policies or nod towards key figures in these racist movements, giving them at the very least verbal support.

“When we say things like: ‘Never again’ or ‘No pasaran’ or ‘Souviens-toi,’ we must make sure we mean it and do what has to be done to stop the forces who dehumanise, persecute and murder people for no reason other than their birth, their background or their religion.”

The anti-fascists will assemble at 11am outside BBC Broadcasting House in Portland Place, central London.