Nearly 50 intruders have set fire to equipment, machinery and cars at the Hellas gold mining site in the Halkidiki region in Greece.
Masked arsonists used flammable liquid and bombs to set machinery and offices alight on Sunday, as fierce opposition to the mine's development continues.
Local citizens and environmentalists have tried to halt the project since 2011, saying it will cause irreversible damage.
The gold mine is under the operation of Hellenic Gold, a subsidiary of Canadian gold mining company Eldorado Gold.
A security guard was reportedly injured in the attack and police detained 27 individuals who were later released.
Eldorado Gold CEO Paul Wright said in a statement that the company respects the right of individuals to voice their opinions in a safe, legal and responsible manner but condemns any activity that risks the safety of employees, contractors and assets.
"The company is in possession of all permits required to operate legally at its projects in Halkidiki. These projects are licensed under an Environmental Impact Assessment, which consisted of an exhaustive technical review as well as comprehensive public consultations.
"In Halkidiki, as in all our mining operations throughout the world, we operate to the highest environmental standards complying with all local, national and international laws and regulations," Wright said.
Following operations to contain the fire and secure the site, the company is now working with the police and local authorities to ensure the ongoing safety of assets and workers.
Scheduled to open in 2015, the mine is expected to generate nearly 5,000 direct and indirect jobs in Greece.
In January 2013, hundreds of Greeks protested against the development of the new mine on the streets of Athens.