Some 40 masked attackers raised a disputed gold-mining project in northern Greece early on Sunday, setting fire to machinery and lightly injuring four security officers, according to a report from Reuters.

The Skouries project has been the target of several protests by locals and activists who say the mine would devastate the environment, the article says.

Police report that the assailants entered the facility at around 12:40 a.m., causing extensive damage with firebombs and flammable liquid. Police also state that 27 people have been detained.