Mineworkers work deep underground at Harmony Gold Mine's Cooke shaft near Johannesburg, September 22, 2005. REUTERS

A four-hour power cut hit Zambia's capital and main mining region on Wednesday, although it was not clear what if any impact there was on output from Africa's biggest copper producer.

Konkola Copper Mines, a unit of London-listed Vedanta Resources, said 220 miners trapped underground were safely evacuated under emergency power.

Production restarted in phases after the interruption and the impact on production would be communicated later, the company said.

State power utility Zesco said Lusaka and the Copper Belt were hit by the black-out, but other mining firms in the region did not respond to requests for comment.

Mining firms in Zambia include Canada's First Quantum Minerals and Barrick Gold and London-listed commodity giant Glencore.

Electricity supply in Zambia is expected to remain tight for the next four years, casting a shadow over the power-intensive mining sector in the southern Africa nation.