Hundreds of men drafted into Eritrea’s army were used as forced labour to build a Canadian company’s copper-gold mine in central Eritrea, according to a former construction official, in a case testing the global responsibility of foreign firms to workers.

Claims of forced labour at the Bisha mine, jointly owned by Nevsun Resources Ltd. and state-owned Eritrean National Mining Corp., date back to 2008 but are now the subject of a class-action lawsuit at British Columbia’s Supreme Court.

Eritrean plaintiffs, living in exile in Ethiopia, say in the lawsuit filed last November that they were forced to build the only operating mine in the Horn of Africa country during national service, enduring filthy conditions, little food or scarce payment.

Although Nevsun was not directly responsible for hiring local staff – that was done through local contractor firm Segen – plaintiffs argue the Canadian company was complicit in their servitude, a claim the Vancouver-based company denies.

Lawyers representing the plaintiffs would not discuss how much money they are seeking from the company.

Although accusations about Bisha date back seven years, this is the first time workers have tried to take legal action outside Eritrea, which lawyers say could act as a warning to foreign companies working with regimes accused of human rights abuses.

“The case is still in its preliminary stages … [but] if the plaintiffs win, it will set a precedent,” University of Ottawa law professor Penelope Simons, a human rights legal specialist, told the Thomson Reuters Foundation.

“So far very few of these types of cases have proceeded to trial … Where a government systematically uses forced labour and a corporation goes into business with that government, there is a significant risk the corporation will become complicit.”

Nevsun has repeatedly stated that none of the workers at Bisha, which started operations in 2011, were army conscripts and said it will “vigorously defend itself” against the lawsuit. The next court hearing is set for January.

But the former construction official, a citizen of another African country, told the Thomson Reuters Foundation by phone that Eritreans conscripted into the military were forced to work at Bisha, 180 kilometres from the capital Asmara.

“There were as many as 500-600 conscripts working in the first round of construction,” the former official said in his first interview since leaving Eritrea, requesting anonymity.

“The heavy machinery operators wore military uniforms in the beginning,” he said, adding they lived in a separate camp.

The Thomson Reuters Foundation could not reach exiled Eritrean plaintiffs for comment.

Eritrea’s Ministry of Energy and Mines, the body responsible for overseeing the Eritrean National Mining Corporation, did not respond to interview requests.

Eritrea introduced compulsory military service in 1995, saying it would benefit the country, which won independence from Ethiopia in 1993 after years of war and deep-rooted poverty.

But human rights campaigners argue the open-ended program – the average service lasts more than six years, according to a 2014 study – constitutes forced labour and thousands of Eritreans flee every year to avoid the draft.

The Eritrean defence ministry, which is responsible for the conscription program, could not be reached for comment.

The use of conscripted labour in mining in Eritrea was first reported by campaign group Human Rights Watch in 2013.