A separatist leader in Indonesia's Papua province has accused the military of mounting an attack which killed two Americans and one Indonesian near the huge Freeport mine.

The army has blamed followers of Kelly Kwalik, a local leader of the disorganized and poorly armed Free Papua Movement (OPM) separatist army for the attack on August 31.

"We are enraged by the shootings which killed three people and injured 14 others," Kwalik said in a hand-written statement received by AFP on Saturday.

"It is better for the TNI [Indonesian armed forces] to admit [that it carried out the attack] and stop its actions," said the statement, signed by Kwalik and sealed with OPM's stamp.

Kwalik accused the army of using native Papuans to wage a mock war against government troops to justify crackdowns on separatists.