Lieutenant Colonel Godhelp Mansnembra, a local police chief, told the Associated Press that two police officers were killed, although he added they were not killed by the attackers.
Another officer who witnessed the incident said that a police vehicle escorting the Freeport employees had flipped over during the ambush.
The latest attack comes a day after police said they had detained 17 people in connection with a spate of shootings near the mine.
At least 15 people, most of them police officers, have been killed or injured in ambushes along roads in the area.
In one attack a 29-year-old Australian miner was shot and killed.
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| Indonesian police and special forces have stepped up security at the mine [Reuters] |
The shootings are the worst violence at the Grasberg mine since the killing of three school teachers, including two Americans, in August 2002.
The massive Grasberg gold and copper mining complex, the world's largest, is majority owned by Freeport-McMoRan Copper & Gold Incorporated, based in the US state of Arizona
The complex employs 20,000 people.
Members of the Free Papua Movement, who see Freeport as a symbol of outside rule, were initially blamed by authorities for the latest violence.
However several analysts have cast doubt on whether the movement has the ability or motivation to carry out such attacks.
Papua, a poor and mountainous province, lies some 3,400km east of the Indonesian capital, Jakarta, and is home to a 40-year-old insurgency that has denounces the Freeport mine as a symbol of outside rule.
Many Papuans are resentful because the mine earns billions of dollars in profit from the region's natural resources, little or none of which makes it back to the local community.