Three Greeks, a Spaniard and a Swiss women were arrested after police raided three squats in Patra, western Greece, on Monday.
The five face charges of causing damage, stealing electricity, disturbing the peace, using violence and breaking weapons laws.
Police raided the three properties, including one owned by the local university and another belonging to Patra Technical College, at 6.30 a.m.
One of the buildings was being used to broadcast a pirate radio station.
Officers seized a substantial amount of broadcasting equipment.
Teams of workmen employed by the local municipality were given access to the buildings to begin repair work.