A proposed gold mine in northern Greece that has sparked heated opposition and an armed attack was the target of another protest over the weekend.

About 20,000 demonstrators opposed to the Skouries project on Greece's Halkidiki Peninsula marched Saturday in nearby Thessaloniki, demanding that the government revoke approvals given to Canadian mine owner Eldorado Gold.

The protesters began the march at 11:30 a.m. at the city's YMCA Square and moved to the White Tower monument and museum, where speakers demanded an end to the Skouries project, which opponents say will destroy the environment of the surrounding woods and cost local livelihoods dependent on tourism, the Greek daily Ta Nea reported.

Speakers at the rally included residents of the city, Halkidiki and Thrace, as well as environmentalists and at least one politician, Greek Member of Parliament Kriton Arsenis, who has frequently spoken against gold mining in the region, the Greek online broadcaster OnAir24.gr reported.

Saturday's rally was peaceful, in contrast to clashes Thursday in Halkidiki, where police used tear gas to break up a demonstration called to protest the arrests of five people suspected of a Feb. 17 break-in at the Skouries site.

Those protests in the village of Ierissos were triggered by news that the five detainees had been transferred there. A member of the Ierissos citizens Committee Against Skouries told a local broadcaster a high school student had been hit in the head with a tear gas canister.

Police, however, denied tear gas was deployed against protesters but only used to clear a roadblock that been preventing police from reaching the village.

The main leftist opposition SYRIZA party criticized the Greek government in Parliament over the incident Thursday, accusing it of using excessive police violence, Kathimerini reported.

The five suspects were arrested in connection with a Feb. 17 incident in which Eldorado Gold said "a masked and armed group of approximately 50 persons" illegally entered the project site, assaulting two of security personnel, with one requiring hospitalization.

Eldorado Gold Chief Executive Paul Wright said the group then set fire to a temporary construction offices as well as several trucks and heavy equipment, most of which were owned by local contractors.

"While we respect the right of individuals to voice their opinions in a safe, legal and responsible manner we fully condemn any activities that put the safety of our employees, contractors and assets at risk," Wright said.

The $1.7 billion Skouries project has received key environmental approvals from the city of Aristoteli, where local officials contend project will be a boon to an ailing Greek economy that is suffering from high levels of unemployment, creating about 1,800 jobs in the area.

"Our aim is to use the mineral wealth of our land and stand on our own two feet," Aristoteli Mayor Christos Pachtas told Kathimerini last year.

But opponents insist the environmental damage from the mine will cause job losses in the tourism, farming, fishing and forestry sectors, which are all highly dependent on the centuries-old, unspoiled forests in Halkidiki.

"This kind of development will destroy a lot more jobs than it will create," Maria Kadoglou of the Anti Gold Greece website told Mining-Technology.com.