Newmont Mining Corp's Indonesian unit said output was unaffected at its copper and gold mine even though 400 workers had gone on strike in a dispute over working shifts.

It is true that around 400 workers are on strike due to working shifts, Newmont Nusa Tenggara spokesman Rubi Purnomo told Reuters on Wednesday, adding the strike began on Tuesday. He did not give detail on the total workforce.

Operation at Batu Hijau is still running as usual and up until today no impact on production, he said. The management and union along with a government representative are having a dialogue.

Batu Hijau, the nation's second-biggest copper mine, aims to produce around 275 million pounds of copper and 275,000 ounces of gold in 2011.

Output at NNT's Batu Hijau mine was unaffected in September after a demonstration by 40 people over job availability at its facilities on Sumbawa island.

Earlier this year, under a contract agreed with the government, foreign shareholders in NNT completed the sale of a 7 percent stake to the government.

The Newmont strike comes at a time of heightened tensions within the Indonesian mining industry, as workers push for a greater share of profits.

Striking workers at Freeport Indonesia's giant Grasberg copper and gold mine, are currently involved in the country's longest-running mining dispute.

Miners at Grasberg, the world's second biggest copper mine, have been on strike since mid-September, leading Freeport McMoRan Copper & Gold Inc to declare a force majeure on concentrate shipments last month.

Benchmark copper on the London Metal Exchange traded at $7,627.75 a tonne at 1118 GMT, versus $7,680 at Tuesday's close. The red metal hit a record high above $10,000 a tonne in February.