A security guard working for U.S. mining giant Freeport was killed and five other people were injured when their vehicles came under attack Sunday in Indonesia's restive Papua province, a company official said.

The incident was near where police units were investigating the fatal shooting a day earlier of a 29-year-old Australian working for the company, Freeport said in a statement to The Associated Press.

Papua, a desperately poor and militarized province on Indonesia's easternmost tip, is home to separatist rebels who denounce PT Freeport as a symbol of Jakarta's rule. The weekend killings come amid an escalation of violence in the region in recent months that has left several security personnel dead.

The Grasberg mining complex, a global supplier of copper and gold that began operations under the Suharto dictatorship, has been a constant source of friction with local Papuans angered over the outflow of profit to foreign investors, while they remain poor.

Two Americans were killed in an ambush in 2002 near the Grasberg operations, a massive open-pit mine that is one of the largest in the world.

On Sunday, "shots were fired at two security vehicles, fatally wounding one (PT Freeport) contract security employee," while five others had minor injuries, the Freeport statement said.

It gave no further details, but Papua police chief Bagus Ekodanto said rebels may have been involved.

"Suspected separatist rebels ambushed and opened fire on the police's anti-terror unit members who were searching for perpetrators" of Saturday's killing, he said.

The people who were shot, including the dead security guard, apparently got caught up in a firefight.

Security has been beefed up at the site since Saturday's killing, but business has not been disrupted, Freeport spokesman Mindo Pangaribuan said.

The Indonesian government does not allow foreign media to freely report in Papua, where it has tens of thousands of troops. The site of Saturday's shooting was inaccessible to local reporters.