Human Rights Watch says Zambia’s president must ensure workers in the country’s Chinese-owned cooper mines are not subjected to unsafe conditions.

The rights group says President Michael Sata has failed to make good on a campaign pledge to enforce and improve copper mining safety regulations.

In a report Thursday, Human Rights Watch outlined poor safety conditions in Zambian mines owned by China’s Non-Ferrous Metals Mining Corporation.

HRW says workers are forced to work shifts lasting from 12 to 18 hours in mines with poor ventilation.

Under Zambian law, miners can work eight hour shifts totaling 48 hours each week.

The rights group says some miners also complained of working without a day off, and those who refused to work risk losing their job.

HRW African Director Daniel Bekele says China has made some improvements, such as providing protective equipment. But he says conditions still fall short of meeting accepted labor standards.

Bekele says while both countries benefit from the cooper industry, it’s up to Zambia’s president to make sure mining laws are enforced to protect the rights of workers.

Human Rights Watch says China’s investment in cooper mining accounts for 75 percent of Zambia’s exports and two thirds of the revenue generated by the government.