The extreme-right, anti-immigrant Golden Dawn is under a criminal investigation regarding last month's fatal stabbing of a Greek rap singer.
Party leader and legislator Nikos Michaloliakos and two other Golden Dawn lawmakers are in pre-trial custody as alleged members of a criminal organization. Six other Golden Dawn legislators, including party spokesman Ilias Kassidiaris, have been stripped of immunity from prosecution.
During Saturday's peaceful protest, Kassidiaris told reporters it was designed to demand the immediate release of Michaloliakos and the two other jailed lawmakers.
An "anti-fascist" rally and march of similar size took place earlier Saturday, and police prevented it from reaching the Golden Dawn rally.