Image copyright PA Image caption Oskar Dunn-Koczorowski, left, and Michal Szewczuk were members of British neo-Nazi group Sonnenkrieg Division which was exposed by the BBC

Two teenage neo-Nazis, who encouraged an attack on Prince Harry for marrying a woman of mixed race, have been jailed for terrorism offences.

Michal Szewczuk, 19, from Leeds, and Oskar Dunn-Koczorowski, 18, from west London, were part of a group called the Sonnenkrieg Division.

An Old Bailey judge said their online propaganda was abhorrent and criminal.

Dunn-Koczorowski was given an 18-month detention and training order. Szewczuk was jailed for just over four years.

The defendants, who appeared by video link from HMP Belmarsh, in south-east London, did not react.

The court heard the teenagers used pseudonyms to run personal accounts on the Gab social media site, as well as sharing control of the Sonnenkrieg Division's own page, on which they posted self-designed propaganda that encouraged terrorist attacks.

Among other things, the imagery suggested the Duke of Sussex was a "race traitor" who should be shot, glorified the Norwegian mass murderer Anders Breivik, and said white women who date non-white men should be hanged.

The material was "uniformly violent and threatening" and "the nature of the violence includes rape and execution", Judge Rebecca Poulet QC said.

Suggested targets included non-white and Jewish people, and the effect was to overtly encourage lone acts of violence against members of the public, the judge added.

She said the men had promoted both Sonnenkrieg and the American Atomwaffen Division, which were extreme right-wing groups inspired by a book called Siege written by the veteran American neo-Nazi James Mason in the 1980s.

Image copyright Reuters Image caption The pair's neo-Nazi propaganda attacked Prince Harry for marrying Meghan Markle

Their ideology is violently racist and anti-Semitic neo-Nazism and its tactics involve political violence through acting alone or small-cell terrorism, she added.

She condemned an "additional feature" of the ideology by referencing a blog run by Szewczuk that encouraged the rape of female adults and babies.

Sonnenkrieg's activities were exposed last year by a BBC investigation.

Prosecutor Naomi Parsons, opening the case earlier in the hearing, told the court: "This isn't a keyboard organisation. It is intent on action."

She read from the group's mission statement, which declared: "Will you rise up and take the chance or will you sit back and do nothing… Hail victory, and Heil Hitler!"

In April, Szewczuk admitted two counts of encouraging terrorism and five of possessing documents useful to a terrorist.

Dunn-Koczorowski pleaded guilty while still a youth in December to two counts of encouraging terrorism.

The court heard Sonnenkrieg was influenced by the US-based group Atomwaffen Division, which is linked to five murders, and Mason, whose writings "may well represent the most violent, revolutionary and potentially terroristic expression of right-wing extremism current today".

'Machine of terror'

Sonnenkrieg promoted the idea that people should completely "drop out" of society and engage in a "total attack" on the system, Ms Parsons told the court.

She said Szewczuk also maintained an "extremely violent and aggressively misogynistic" blog that encouraged the rape, torture and murder of women and babies.

"You must become a machine of terror," Szewczuk had advised his readers.

Image copyright Hope not Hate Image caption Dunn-Koczorowski joined the now banned terrorist group National Action as a schoolboy

In online comments, Dunn-Koczorowski suggested that decapitating babies would be acceptable to stop them becoming "leftist politicians" and proclaimed "terror is the best political weapon for nothing drives people harder than a fear of sudden death".

The pair were arrested the morning after the BBC investigation was broadcast in December.

Detectives found Szewczuk - then a computer science student at the University of Portsmouth - in possession of bomb-making instructions, documents describing how to conduct Islamist terror attacks and a "white resistance" manual.

A man from Bath arrested on the same day has been released under investigation and a file of evidence sent to the Crown Prosecution Service for a charging decision.

It is understood that Dunn-Koczorowski joined the now banned terrorist group National Action as a schoolboy and later played a role in two successor organisations before taking up with Sonnenkrieg.

The court heard he had breached his bail conditions in May by using social media to post about his extremist ideology.

The judge said he was in no sense showing "remorse", which was "very concerning".

"You still hold deeply entrenched views in support of this extreme right wing ideology," she told the teenager.

Det Chief Supt Martin Snowden, head of counter terrorism policing in the north-east of England, said Dunn-Koczorowski and Szewczuk clearly saw themselves as superior to the majority of society and they felt it was their duty to express their beliefs, in turn teaching others.

He told the BBC it "only takes one individual to be encouraged or be inspired by that propaganda to take that further step" and this "represents a significant risk".

Hitler imagined as avatar of a god

By Daniel De Simone, BBC home affairs producer

Sonnenkrieg Division, which police say has the most radical ideology on the UK extreme right, is the latest neo-Nazi group to emerge following the proscription of National Action under anti-terror laws three years ago.

Created by a small number of people, Sonnenkrieg used the internet to exaggerate its size and capabilities, with members seeking direct action from those accessing its propaganda.

Terrorism and criminality were encouraged, as was the transgression of what it caricatured as slavish morality, with sexual violence and paedophilia both advocated.

Their bizarre supernatural belief system imagined Hitler to be an avatar of a god, lionised the Moors Murderer Ian Brady and cult leader Charles Manson, and blended violent Satanism, a berserk misogyny, and admiration for radical Islamism.

The aim? To undermine and collapse civilization, which the group deemed a necessary forerunner to the creation of a Nazi warrior society.