The new offices of the Party of Equality, Peace and Friendship (KIEF) in Komotini, northeastern Greece, were attacked on Tuesday.
Assailants smashed windows at the building, broke a photocopier and daubed “Sentries of Thrace” on the wall.
KIEF was founded in 1991 by Sadik Ahmet, a leading member of Greece’s Muslim minority.
Ahmet was killed in a car crash in July 1995.
The vehicle had been kept by KIEF as a memorial and had also been transferred to the new premises but was stolen by the assailants.
The Greek Foreign Ministry condemned the incident.
“Incendiary actions such as this are in full opposition to the spirit of peace and cooperation that have long characterized the coexistence of Christians and Muslims in Thrace,” it said.
“The competent Greek authorities will immediately proceed to the necessary actions to get to the bottom of the incident and bring the perpetrators to justice.”
KIEF had only recently rented the new building and had not yet moved its operations to the site, located on the outskirts of Komotini.