Unknown perpetrators splashed black paint on the external walls of the US ambassador's residency in Athens on Wednesday.
The anarchist group Rouvikonas [Rubicon] reportedly claimed responsibility for the act.
The perpetrators are said to have arrived around 4 a.m. with motorcycles. Upon throwing the paint, and reportedly a smoke bomb, they promptly escaped.
US Ambassador to Greece Geoffrey Pyatt condemned the act on social media, saying it was "childish vandalism."
According to reports, this is the third time that the US ambassador's residence has been targeted by anti-establishment groups.