The U.S. owner of a gold and copper mine in eastern Indonesia that is among the largest in the world says its operations have been disrupted by a days-long strike.

Freeport-McMoran spokesman Riza Pratama said Monday that open pit mining has stopped and processing of ore has been reduced.

A union official, Frans Okoseray, said about 1,200 workers began their strike on Wednesday to get bigger monthly bonus payments.

The Grasberg mine in Indonesia's Papua province is the world's largest gold mine by reserves and one of the largest copper mines.

Okoseray said the strikers include heavy equipment operators and truck drivers. He said they want their bonus to be equal to underground mine workers who get a 50 percent bonus each month.

Pratama said underground mining hasn't been affected.