Greek neo-Nazi party Golden Dawn has sued the police for breach of duty, alleging that overzealous officers illegally entered party premises to arrest over a dozen members, police said Thursday.
The complaint was filed after a Communist unionist claimed to have been roughed up outside a rural Golden Dawn office near Athens on Tuesday.
Police briefly detained 15 party members but later set them free. They deny illegal entry.
Golden Dawn, formerly on the fringe of Greek politics, has seen its ratings soar since last year in a country weary of austerity and political corruption.
The party saw 18 deputies to parliament in June for the first time in its history and is currently the third most popular party in opinion polls.
The party has a military-style discipline and wastes no opportunity to attack Greece's political establishment as corrupt and obsolete.
In January, Golden Dawn said that even Greece's respected president Carolos Papoulias was part of a "noble class" of "traitors and sold-out politicians."
Its lawmakers, mostly picked for brawn over eloquence, often use street language and aggressive behaviour to intimidate opponents.
Three of them are scheduled to be tried for assault against migrant peddlers.
A fourth is also to face justice for assaulting two left-wing deputies during a talk show.
Rights groups have regularly accused Greek police of turning a blind eye to suspected Golden Dawn attacks.