Eldorado had appealed to Greece's top court to overturn a ban on its plans to develop a gold mine in a forested area of northern Greece, in a case widely seen as a test of the leftist government's approach to foreign investment.

The Vancouver-based gold miner's venture to extract gold and other ores on the verdant Halkidiki peninsula is seen as one of the top investments in a country racked by a debt crisis since the end of 2009.

The court canceled on Friday an energy ministry decision that halted operations in Halkidiki until a final ruling is made later in October, favoring an appeal by workers at the mining company.

The company said after the ruling that it planned to resume operations and call its workers back to work.

"As soon as we are officially notified of this court ruling we will bring our workers back to work," Eldorado's country manager for Greece, Eduardo Moura, told Reuters.

Eldorado has put in more than $600 million since 2012 and plans to invest another $1 billion in its quest for gold, copper and zinc in the region.

But after Greece's left-wing government revoked its permit in August, citing environmental grounds, Eldorado suspended all its activities at the mine and made two thirds of its 1,300 workers temporarily redundant.

"The court weighed the loss claimed by the workers against the argument of the state and overturned the decision of the energy minister," a court official said.

"For the 867 workers of 'Hellenic Gold' the court ruled that the minister's decision would have caused them substantial losses as they would be made redundant or lose their jobs."

Some 500 workers demonstrated on Friday in support of the company's appeal outside the Council of State, Greece's highest administrative court, some carrying a banner that proclaimed: "No future without the ores".

(Reporting by Angeliki Koutantou and George Georgiopoulos,; Editing by Elaine Hardcastle and Adrian Croft)