Police detained 19 suspects on Wednesday after members of the anti-establishment group Rouvikonas (Greek for Rubicon) barged into the Spanish Embassy in Athens.
In a message posted on the Athens Indymedia website, the group said the raid, which took place shortly after 10 a.m., was in solidarity with “the oppressed people of Catalonia.”
There were no reports of injuries but reports suggested the assailants caused damage to the building on the Dionysiou Areopagitou promenade, near the Acropolis in the center of the Greek capital.
On Tuesday, Catalan President Carles Puigdemont and other regional leaders signed a declaration of independence from Spain, following a controversial referendum on October 1.
However, they said the move will not be implemented for several weeks to allow talks with the government in Madrid.