Less than a week after Zambia, Africa's largest copper producer, lifted the 10% export levy on unprocessed copper concentrates to allow mining companies release surplus stocks, the government announced Monday it has reinstated a modified version of it.

The move comes after President Michael Sata said the law suspending taxes on raw materials, announced last Wednesday, would not benefit the country.

Instead, Zambia has introduced a 10% export duty on semi-processed base metals, including copper, Secretary to the Treasury, Fredson Yamba, told Reuters.

Mining companies operating in the African nation continue to be battered by low global copper prices, which have been weighed by signs of reduced Chinese demand and higher global production.

The country's copper production is expected to rise to 1.5 million metric tons, from around 800,000 tons produced in 2012, as more projects come on stream.