Production has halted at a China National Nuclear Corporation (Sino-U) uranium mine in northern Niger as workers downed their tools for a 72-hour strike.

On Tuesday, Boubacar Mamane, a spokesman for the Syntramines labor union, said 680 workers at Sino-U would be on strike until their demands for better wages and a bonus system are met.

“Management refused to pay our allowances and production bonus despite having promised to do so last year. If nothing is done, we will launch an unlimited strike,” Mamane said.

Sino-U officials and the Nigerian government, which owns 33% of the mine, were not available to comment, reports Reuters.

Sino-U, China’s largest nuclear plant operator, and its partners holds a majority stake at the Somina mine, which was established in 2007 in the Agadez region of northern Niger. The mine has produced 700 tonnes of uranium annually since it began production in 2011 and is expected to ramp up output to 2,500 tonnes annually in 2015.

The acquisition comes as China increases efforts to secure more of the metal used in nuclear power production, China Daily reports.

The West African nation is the top supplier of uranium to France’s nuclear power industry, Press TV reports.