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Miners from Eldorado gold mine in northern Greece argue with riot police today. Photograph: Louisa Gouliamaki/AFP/Getty Images

Anger in the streets if Athens boiled over this morning with police firing tear gas at protesting workers from the Canadian-owned Eldorado Gold mine company.

Helena Smith reports from Athens.

Police fired off rounds of tear gas at an estimated 100 workers protesting against potential job losses outside the energy ministry.

Officers said they took the unexpected action after demonstrators attempted to storm the building shouting: “we won’t leave until workers permits are handed out.”

AP Business News (@APBusiness) Greek gold miners clash with police in Athens as doubt hangs over major investment. Video by @SdrjanTV https://t.co/Bg99DUy0es pic.twitter.com/uQaRsOZrH9

Tensions have mounted since the Vancouver-based company threatened to pull out of Greece – effectively dismantling the country’s biggest foreign investment – because of endless delays in procuring permits.

George Burns, Eldorado’s chief executive, announced that operations would be halted on Monday only hours after prime minister Alexis Tsipras said his leftist-led government would do everything it could to welcome foreign investment. Under his personal stewardship, he said, a task-force dedicated to “Grinvestment” would replace fears of Grexit.

Around 2,000 people are employed by Eldorado which says its Skouries and Olympias projects in northern Greece have the potential to make Greece a leading European gold producer. Environmental concerns have prompted violent protests in what has become a test case of the government’s resolve to attract foreign investors.

And in the last few minutes, the government appears to have caved in and said it will be issuing licenses for Eldorado to press ahead with investments in northern Greece.

The energy minister Giorgos Stathakis said necessary paperwork “will be concluded in the coming days, today and tomorrow. Three permits will be issues ... allowing Olympias to be fully operational.”