Union president Joseph Chewe told Reuters the company informed them of the layoffs, and said it was halting production temporarily due to difficulties sourcing raw materials for the refinery. Zambia's mines minister Richard Musukwa also confirmed the layoffs.

The Chambishi Metals refinery has a capacity of 6.8 kilo-tonnes per annum of cobalt metal and 55 kilo-tonnes per annum of copper metal. ERG did not immediately reply to a request for comment.

(Reporting by Chris Mfula, Writing by Helen Reid, Editing by Elaine Hardcastle)