The leader of Greece's extreme-right Golden Dawn party and four other of its parliamentarians have been formally charged with membership of a criminal organisation with intent to commit crimes.
It was the first time since 1974 that sitting members of Parliament have been arrested. The arrests underline the Greek government's efforts to stifle the fiercely anti-immigrant party.
Golden Dawn leader Nikos Michaloliakos, party spokesman Ilias Kassidiaris and Yannis Lagos, Nikos Michos and Ilias Panayiotaros were arrested by counter-terrorism police. The last two gave themselves up voluntarily. A sixth parliamentarian, Christos Pappas - described in a prosecutor's report as the Golden Dawn's number two - remains at large.
A further 15 people, including 13 Golden Dawn members and two police officers, have also been arrested and are due to appear before a prosecutor and an examining magistrate soon. They face the same charges.
Police spokesman Christos Pagonis said that the counter-terrorism unit was still searching for the 12 suspects at large, including the missing deputy.
"It is an unprecedentedly dynamic response to a neo-Nazi organization," government spokesman Simos Kedikoglou said, hinting the arrests were the culmination of a long strategy to deal with Golden Dawn as a criminal, not a political force.
"The prime minister and the government were determined to deal with Golden Dawn solely through the justice system ... We have succeeded in stripping them of their political cover and deal with them as what they really are, a criminal organization," Mr Kedikoglou said.
Citizen protection minister Nikos Dendias compared Golden Dawn members to German SS squads.
"The state has proven it is not helpless in the face of organised violence ... Greek society will not tolerate any storm troopers," Mr Dendias said.
The government ordered an investigation into Golden Dawn's activities after the death of rapper Pavlos Fyssas on September 18 sparked outrage across Greece.
The suspect arrested over his death admitted to police that he had stabbed the 34-year-old and identified himself as a supporter of Golden Dawn. Police investigated his mobile phone records and those of more than 300 people connected to Golden Dawn.
Investigations have extended to the police, who have been accused in the past of turning a blind eye to Golden Dawn violence and of mistreating immigrants.
Under existing anti-terrorism legislation, membership in a criminal organisation is a flagrant crime for which the Golden Dawn deputies can be prosecuted without Parliament needing to lift their immunity.
Despite the arrests, the party's lawmakers retain their parliamentary seats unless they are convicted of a crime. Golden Dawn holds 18 of Parliament's 300 seats, after winning nearly 7% of the vote in general elections last year.
The party has vehemently denied any role in the killing, but it has appeared to dent Golden Dawn's appeal among Greeks. As calls for a crackdown mounted, the party hinted its parliamentarians might resign to provoke elections in 15 multi-party constituencies.
"There will be no elections, certainly no general elections," Mr Kedikoglou said. Asked about the likelihood of partial elections if Golden Dawn deputies were to resign, he said "there are ways to deal with that, as well."