Mali is the third biggest gold producer in Africa behind South Africa and Ghana, and gold overwhelmingly dominates its mining sector, itself about a quarter of government revenues.
"Trade unionists are persecuted in the mines," said Mahamadou Konte, executive committee member of Synacom, the mines, energy and civil construction union, citing examples of union members who were being disciplined or fired.
"We represent more than 80 percent of the union space. The strike will affect all mines," he said.
The likely impact on production from the country's nine gold mines was unclear, but Konte reckoned that the strike would cost Mali 800 million CFA francs ($1.37 million) per day in tax revenues.
Mali collected 245 billion CFA francs ($422 million) in state revenues from mining companies last year, a near 11 percent fall from the previous year, owing to stagnant production and lower gold prices, the statistics office said in August.
Gold producers including Randgold Resources and AngloGold Ashanti have operations in Mali.