The trial of the leadership and dozens of members of Greece's extreme right Golden Dawn party has resumed, with the defendants facing charges of operating as a criminal organization that conducted a campaign of beatings and stabbings against migrants and left-wing opponents.

The case against 69 people including party leader Nikos Michaloliakos and members of parliament is being heard under tight security in a special courtroom in Greece's largest prison, Korydallos.

Thursday's session was the second day of the trial, which was postponed after its initial opening last month for procedural reasons.

Michaloliakos, who is under house arrest after serving the maximum allowable 18 months in pre-trial detention, was not present. The court was again dealing largely with procedural issues.

Hundreds of anti-Golden Dawn protesters gathered outside the prison.