Operations at Freeport Indonesia's copper mine in Papua have been affected as more than 50 employees have blocked access to the facility.
Freeport union senior official Albar Sabang told Reuters that the blockade also includes locals who are not employed by the company.
It is believed that workers from seven mining areas in Papua decided to express their disappointment with Freeport's management, accusing it of firing and suspending their colleagues who recently went on strike.
A union spokeswoman said: "The blockade that is currently happening is being done outside the workers union and was not organised by the union."
The news agency also reported the spokeswoman as saying that, despite the strike, the situation at the mine was not unsafe.
Earlier this week, Freeport said it believed the matter could be settled without causing a major effect to production.
Located in the province of Papua in Indonesia near Puncak Jaya, Grasberg copper mine employees 19,500 people.
The mine is majority-owned by Freeport-McMoRan, which has a 90.64% interest in PT Freeport Indonesia, the principal operating subsidiary in Indonesia. This also includes 9.36% held through its wholly owned subsidiary, PT Indocopper Investama.
The Government of Indonesia owns the remaining 9.36% of PT Freeport Indonesia, which is the local unit of US-based mining company Freeport-McMoRan.
The company, which employs around 24,000 workers, is expected to produce 43% more copper concentrate this year than before, at two million tonnes.
Image: Grasberg copper mine sits in the province of Papua in Indonesia, near Puncak Jaya. Photo: courtesy of Alfindra Primaldhi.