Nine people were injured on Sunday during clashes with police at a protest against a controversial Canadian gold mining project in northern Greece, the Athens News Agency reported.
Eight riot police officers and one female activist were wounded during the protest at the site of Hellenic Gold, in the popular tourist region of Halkidiki, according to the state-run agency.
Four of the officers were injured after being shot at.
Three people were detained in connection to clashes, a police source said.
"Shooting police officers in Halkidiki is a major challenge against the state of justice in our country," Public Order Minister Nikos Dendias said in a statement released later on Sunday.
Civil groups have been trying to halt the project since 2011, when the Greek government gave the company -- a subsidiary of Canadian firm Eldorado Gold -- permission to dig in the region.
Protesters claim the project will cause irreversible harm to the environment, draining and contaminating local water reserves and filling the air with hazardous chemicals including lead, cadmium, arsenic and mercury.
Several protest rallies have taken place in recent months.
In February, activists firebombed the Hellenic Gold site, injuring a guard and damaging equipment.
In April, angry locals trashed a police station over claims officers had used excessive force in the pre-dawn arrest of a pair suspected to be linked to the February sabotage attack.
The government supports the investment, which is expected to create hundreds of jobs in the recession-hit country where the unemployment rate now stands at 27 percent.