Chinese mining companies in Zambia ignore labour protections, demanding up to 18 hours of labour a day and flouting health and safety rules, Human Rights Watch said in a report Thursday.

"China's significant investment in Zambia's copper mining industry can benefit both Chinese and Zambians," said Daniel Bekele, Africa director at Human Rights Watch.

"But the miners in Chinese-run companies have been subject to abusive health, safety, and labor conditions and longtime government indifference."

Four Chinese-run copper miners in Zambia are units of the state-owned China Non-Ferrous Metals Mining Corporation, under the authority of China's highest executive body, the report said.

Zambia, Africa's biggest copper producer, has welcomed Chinese investment — though workers have often complained of sub-standard labour conditions.

The report was based on interviews with miners between November 2010 and July 2011.

They described poor ventilation in the shafts, which can cause lung disease, failure to replace damaged equipment, and threats to fire workers who refuse to work in dangerous places.

"They just consider production, not safety. If someone dies, he can be replaced tomorrow. And if you report the problem, you'll lose your job," one miner said in the report.

"Many of the poor health and safety practices we found in Zambia's Chinese-run mines look strikingly similar to abuses we see in China," Bekele said.

"Respecting labor laws and ensuring workers' safety should be standard operating practice both in China and abroad, not treated as an irritating barrier to greater profits."

Many miners at Sino Metals are required to work 12-hour shifts, five days a week, with a sixth 18-hour shift — despite Zambian laws requiring a 48-hour work week, the report said.

Chinese firms have made some improvements since they started working in Zambia in 2003, such as providing safety equipment, but the report said the equipment was sometimes incomplete and not replaced when damaged.

Zambia's Labour Ministry has added to the problem by endorsing contracts that violate labour laws, the report added.

Zambia's new President Michael Sata has vowed to clean up the mining industry and to improve the lives of the poor.

China has invested an estimated $6.1 billion (4.3 billion euros) in the southern African nation since 2007, equivalent to more than one third of gross domestic product last year.