Workers on strike at Bolivia’s biggest tin mine, the state-run Huanuni operation, have cost the mine US$5 million in lost output since they walked off the job on May 6, Reuters reported, quoting a government statement released last Friday. Miners at the mine have joined a general strike to demand better pension benefits, organized by Bolivia’s Central Obrera Boliviana (COB) labour confederation. Miners, teachers and health workers have marched in central La Paz as part of the same campaign, but the miners union agreed to withdraw from the capital on Wednesday after obtaining some assurances on a review of the country’s pensions law.

The protest at Huanuni is the biggest since leftist President Evo Morales renationalized the mine in 2006, and is also affecting production at the Vinto smelter.

The Huanuni mine has produced between 9,500 and 10,000 tonnes of tin-in-concentrate in recent years. The COB, which formerly backed Bolivia’s President Evo Morales, has been campaigning since May 7 for pension increases linked to salary rises, which the government says is unsustainable. It is strongly resisting the strikes, and appears to retain wider popular support.