Arsonists set fire to an office of Greek neo-Nazi party Golden Dawn in central Athens on Monday, causing extensive damages, a police source told AFP.
The incident comes the day after a young Iraqi was knifed to death by five men in a probable hate attack that many blamed on the party.
Located on the fourth floor of a building in the busy neighbourhood of Pangrati, Golden Dawn's offices were empty at the time of the attack and there were no victims, the source said.
The fire was caused by flammable liquid, which the unknown perpetrators lit outside the front door of the offices after entering the building, the source added.
Police are investigating the fire.
The Golden Dawn (Chryssi Avgi) issued a press release condemning what it called "yet another terrorist attack" and added that "the national struggle will continue just as powerfully until Greece belongs once more to the Greeks."
The Golden Dawn, which won 18 out of 300 seats in June, is the first neo-Nazi party to be elected to parliament in Greek history.
The party is suspected of being behind a number of xenophobic attacks on immigrants, which have recently increased.
The Council of Europe's human rights commissioner Nils Muiznieks has called on Greece to examine whether the party is legal.
Mr. Muiznieks has called Golden Dawn the "most overtly extremist and Nazi party in Europe."