Members of Greece's far-right Golden Dawn party have appeared before an Athens investigating magistrate charged with founding and participating in a criminal organisation.
The handcuffed detainees including the leader Nikos Michaloliakos were taken under high security to the prosecutors' office and were charged officially early this morning.
The group who spent the night in jail includes five MPs and 15 other party members.
They were held after a swoop on the party after the killing of an anti-fascist rapper by a party supporter on 17 September and the killing of an immigrant earlier this year, according to court officials.
The investigating magistrate will determine at a later stage which of the suspects would be further charged with leadership, or with illegally possessing weapons.
In the most significant crackdown on a political party in Greece since the fall of a military dictatorship in 1974, the arrests are the biggest setback to Golden Dawn since it entered parliament on an anti-immigrant agenda last year.
Ranked as Greece's third most popular party, it is under investigation for the murder of hip hop artist Pavlos Fissas, who bled to death after being stabbed twice by a party sympathiser.
The party has denied any links to the killing and its arrested leader has warned that Golden Dawn could pull its lawmakers from parliament if the crackdown does not stop.
The anti-terrorism force, which was handling the case, was still looking for senior party official and lawmaker Christos Pappas, according to police officials.
Two police officers were also arrested yesterday.