Between 10 and 15 members of the Rouvikonas anti-establishment group stormed the town hall of Ilioupoli in southern Athens on Wednesday and had an altercation with Mayor Vassilis Valasopoulos and his staff.
Police said they detained at least one individual in connection with the incident. In a post on an anti-establishment website, the group claimed responsibility, saying it was protesting against a string of work-related accidents which it blames on the negligence of the municipal authority.
Separately on Wednesday, a group of self-styled anarchists tried to force their way into an Athens appeals court, disrupting an appeal by the convicted murderers of Shehzad Luqman, a 27-year-old man from Pakistan who was murdered in Petralona in 2013 while riding his bicycle to work.
According to reports, the protesters threw fliers and shouted slogans before being pushed back by police officers.
Christos Steriopoulos, 34, and Dionysis Liakopoulos, 29, were originally convicted to life sentences for the murder in 2014.