Canada's Eldorado Gold Corp (ELD.TO) said it had received an arbitration notice from the Greek government alleging that the technical study for a metallurgical plant is deficient and thereby violates environmental terms for the project.

Eldorado's investment in northern Greece is among the biggest since the country's debt crisis began seven years ago and has long been viewed as a litmus test of Greece's resolve to attract foreign capital.

However, differences with the country, especially over compliance with environmental regulations, have dragged on for years.

The miner had threatened to suspend a major investment in the country, which led to an angry protest outside the energy ministry on Wednesday by dozens of Eldorado Gold workers worried about potential job losses.

Eldorado had earlier said it would halt new investment at its Olympias and Skouries projects from Sept. 22 due to permit delays and lack of clarity on the upcoming arbitration process.

The arbitration notice relates to the company's Madem Lakkos metallurgical plant for treating Olympias and Skouries concentrates in the Stratoni Valley, submitted in 2014, Eldorado said.

"We will vigorously defend our rights and employ all legal means at our disposal," George Burns, Chief Executive Officer of Eldorado Gold said.