Members of the anarchist group Rouvikonas (Rubicon) used sledgehammers to attack the offices of the Attica regional authority in the early hours of Monday morning.
According to the police, serious damage was inflicted at the main entrance of the building at Syngrou Avenue, Athens. The anarchists also sprayed the building with red paint.
No arrests were made.
The group posted a video of the raid on social media, saying that the act was in response to the deadly floods in Mandra, on November 15.
The group, which has carried out dozens of similar attacks on state agencies and other perceived targets, blames the regional authority for the deaths of 23 people.
On November 17, members of Rouvikonas evaded security and invaded the courtyard of the Greek Ministry of Defence.