Leaders of the neo-fascist Golden Dawn have been targeted in early morning raids by Greek counter-terror police, with the party's leader, three MPs and more than a dozen members taken away in handcuffs.
Human rights groups accuse Golden Dawn, the country's third biggest party, of orchestrating violent attacks on immigrants, gays and left-wingers across Greece. Its emblem resembles that of a swastika.
A 45-year-old has been arrested on suspicion of murder, a man rumoured to be a member of the party, which Golden Dawn strongly denies.
Greek media quoted Golden Dawn leader and founder Nikos Michaloliakos shouting when he was arrested: "What you are doing is not right. The truth will shine".
Arrested with him was party spokesman Ilias Kasidiaris, infamous for a violent assault on two female opposition MPs, live on TV.
"Shame on them, the people will lift Golden Dawn higher," Kasidiaris told reporters as he was led away, according to Reuters.
Those arrested are expected to be charged with forming a criminal organisation.More than two dozen count terror units were involved in the operation to track down the organisation's key members.
After the raids, the party rallied its members by text message, hundreds of whom turned out to the police headquarters in Athens, dressed in black.
The text read, according to the BBC: "We call upon everyone to support our moral and just struggle against the corrupt system!"
Police are examining three guns, including a hunting rifle, found at Michaloliakos' home, among other weapons found in the raids.
The crackdown is unprecedented. Indeed, in the weeks preceding the raids, two senior police generals resigned and several others were suspended because of alleged links with the party.
Golden Dawn has been polling at around 15%, and has claimed to have more than one million members.
Earlier this week, Michaloliakos had warned the "mud-slinging and slander" must stop or the party would "open the gates of hell".