Earlier this week, Freeport-McMoran spokesman Riza Pratama said that open pit mining had stopped and processing had been reduced. The underground operation had not been affected.

Union official Frans Okoseray said about 1200 workers began thee strike to get bigger monthly bonus payments. The surface workers want their bonuses to be equal to those of underground mine workers, who received a 50% bonus every month, Okoseray said.

Grasberg is the world's largest gold mine by reserves and one of the largest copper mines.