Workers at the Richards Bay Coal Terminal in South Africa rejected its latest wage offer and will continue to strike, according to the main labor union at the port.

Members of the Association of Mineworkers and Construction Union lowered their demand to a one-year 7% basic salary increase and a housing allowance, said Bheki Sithole, the union’s regional secretary. RBCT, the biggest coal export facility on the continent, offered a minimum 6% annual increase for three years.

Volumes shipped at RBCT have dropped to the lowest level in decades because state-owned ports and rail operator Transnet SOC Ltd.’s operations have been hobbled by sabotage, cable theft and aging equipment. The walkout by RBCT workers that began Sept. 17 isn’t affecting operations, Sithole said.

The company’s offer is final and “does not take into consideration the prevailing rail challenges,” it said in an emailed response to questions. Volumes have dropped to an annualized rate of 46.5 million tons a year, the lowest since 1992, according to RBCT.

Glencore Plc, Thungela Resources Ltd. and Exxaro Resources Ltd. are among companies that use the terminal to ship coal.

RBCT said violent incidents have accompanied the strike, including attacks on employees. Sithole denied such actions.