The Africa subsidiary of Barrick Gold Corp. says it is losing more than $1-million (U.S.) in daily revenue as Tanzania extends an export ban and accuses mining companies of massive tax evasion.

Acacia Mining, majority-owned by Toronto-based Barrick, is the biggest company caught up in the growing furor over Tanzanian allegations that the miners have been misstating their gold production by a huge amount.

The controversy is part of a wave of resource nationalism across Africa, with many governments convinced they are being cheated by foreign investors as a result of misinvoicing schemes and sweetheart deals on taxes and royalties.

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Barrick says it might have to revise its full-year forecasts as a result of the dispute. "In total, Acacia accounts for approximately 10 per cent of Barrick's 2017 gold production guidance," Barrick said in a statement.

Tanzania halted the export of gold concentrate on March 3, saying it wanted more of its gold to be processed inside the country as a way to create jobs, revenue and technology. Since then, Acacia has been trying to resolve the dispute without success.

The dispute escalated last week when Tanzanian President John Magufuli said an investigation had found evidence of Acacia "under-invoicing" the gold and other minerals in the shipping containers in its exports. In the same televised speech, he announced the firing of his mining minister and the chief of the state-run mineral audit agency as a result of the investigation by the presidential committee.

Acacia strongly denies any wrongdoing, noting that its production and finances are audited to international standards by independent auditors.

In a statement on Friday, it said the "combined direct impact" of the export ban is an average daily loss of more than $1-million in revenue at two of its Tanzanian gold mines, Bulyanhulu and Buzwagi. "As a result, we are considering all of our options," the company said.

There are huge discrepancies between Tanzania's allegations and the company's own independently verified data, Acacia said. These data suggest the gold content of Acacia's concentrates is less than one-10th of the amount alleged by the Tanzanian investigation, it said.

"If the [presidential] committee's published findings were based on accurate data, Bulyanhulu and Buzwagi would be the world's two largest gold producers," Acacia said.

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If the allegations were correct, it said, Acacia would be the world's third-largest gold producer, with more gold produced at its three mines than AngloGold Ashanti produces from 19 mines.

"If the committee's findings were accurate and Buzwagi produces and sells 10 times more gold than it declares, Acacia would be extending mining at Buzwagi for many years. The reality is that Buzwagi is a low-grade mine and is running out of commercially viable gold."

The company called for an independent review of the gold content of its concentrates to check the Tanzanian committee's findings. Barrick, meanwhile, said it is "offering Acacia its full support as Acacia works to resolve this matter with the government of Tanzania."

Acacia has been stockpiling the concentrate it cannot export since the ban was imposed, but some analysts have suggested it will be forced to consider a suspension of operations at one or two of its mines.

In March, three weeks after the export ban was imposed, a potential $4-billion merger between Acacia and Toronto-listed Endeavour Mining Corp. was called off. The merger talks had been first confirmed in January.