Gunmen killed a security guard working for U.S. mining conglomerate Freeport on Sunday, then ambushed police responding to the attack blamed on separatist rebels in one of Indonesia's most underdeveloped and remote regions.

The assaults outside the Grasberg mining complex in Papua were in the same area where authorities 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.

The escalation in violence in the region is an unwelcome development for Indonesian President Susilo Bambang Yudhoyono, who was re-elected just last week to a second 5-year-term. It also raised questions about a possible resurgence of Papua's secessionist movement, which until recent months had shown few signs of life.

The rebels see PT Freeport as a symbol of Jakarta's rule and a reminder that foreign investment in the area has failed to lift their standard of living.

The security guard, working on a contract for Freeport, was killed in an ambush by suspected rebels Sunday morning when "shots were fired at two security vehicles," Freeport said in a statement. Five others were injured.

Police units responding to the gunfire were ambushed by suspected rebels near to the scene of the first shooting, said national police spokesman Sulistyo Ishak.

"The attackers opened fire from distant hills, making it difficult for the police to return fire," he said. Two police officers were hospitalized with gunshot wounds, he said. That attack was also blamed on suspected Papuan rebels, but no proof was provided.

The Australian mining expert was shot and killed on Saturday while traveling in a vehicle in the same area. Several other people in the car were unharmed, leading police to conclude the attack may have been the work of a rebel sniper.

No arrests have been made in connection with the shootings, police said.

The weekend killings come amid an escalation of violence in Papua -- a desperately poor and militarized province on Indonesia's easternmost tip -- 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.

Security has been beefed up at the site since Saturday's killing and employees were advised not to travel to Timika, the town closest to the mine. Business was otherwise not 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.