(Bloomberg) -- Africa’s biggest port for iron-ore shipments has all but ground to a halt as about 90% of employees stayed away seeking higher wages. 

Staff at Transnet SOC Ltd., South Africa’s state-owned logistics company which operates most of the harbors in the nation, are refusing to work unless the company agrees to its demand of a pay hike. 

On Monday, about 10% of workers were in attendance at the Saldanha terminal north of Cape Town, which has a capacity to export 57 million tons of iron ore a year, according to a letter Transnet sent to its customers seen by Bloomberg.

The labor action that started with Transnet’s biggest union on Oct. 6 and grew to include more organizations has curtailed the amount of workers, or so called manning levels, to 13% or less at most of its bulk and break-bulk terminals, according to the letter signed by Michelle Van Buren Schele, general manager of commercial and planning.

Transnet “continues to provide shipping services to all terminal operators, and to Transnet Port Terminals where they are able meet manning levels,” the company said in a reply to questions. “The situation differs from terminal to terminal in terms of availability.”

Coal and iron ore miners have warned that a prolonged strike will curtail exports and hobble output. Russia’s invasion of Ukraine has boosted demand for the dirtiest fossil fuels and revitalized a shipping route to Europe. South Africa is also the world’s second-largest exporter of citrus fruit after Spain.

Shares in Thungela Resources Ltd., South Africa’s biggest shipper of thermal coal, fell 5% at 3:14 p.m. in Johannesburg, while Kumba Iron Ore Ltd. fell 0.3%.

“We are closely monitoring the situation and remain focused on doing all we can to minimize the impact of the strike action on our affected customers,” a spokesperson for A.P. Moller-Maersk A/S said in an email, adding that the matter was for Transnet and the unions to resolve.

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