An Indonesian and a Chinese worker died after a clash broke out following a protest staged by a labour group at PT Gunbuster Nickel Industry (GNI) smelter, according to the Central Sulawesi police spokesperson Sr. Comr. Didik Supranoto.

Local media reported the protesters had demanded better safety conditions and pay. 

Several company vehicles were torched and about 100 rooms at workers' dormitories were damaged, Didik said, adding that 71 people had been detained.

Operations at GNI are currently suspended, Didik added. He did not say when they will resume. 

GNI said in a statement the company and police are conducting a investigation into the incident.

"The company, together with law enforcement officials, has immediately launched an in-depth and thorough investigation into the incidents that have caused harm to all parties, both material and immaterial losses, and even fatalities," it said.

GNI launched the smelter in late 2021 with an annual capacity of 1.8 million tonnes and total investment estimated at $2.7 billion. 

Violent protests have broken out sporadically in the mineral-rich region of Sulawesi, which has seen a recent investment boom in nickel that is used in electric vehicle batteries.