Amnesty International says that Indonesian troops have reportedly tortured villagers and torched homes during a hunt for separatist rebels in Papua province.
The rights group says in a statement that a local human rights activist who was briefly detained by the military in Wamena on Saturday reported seeing at least 20 people in detention.
Amnesty says many of the detainees were reportedly injured as a result of being tortured.
It says a number of other people were beaten, houses broken into and possessions stolen and that nine houses were burnt down.
Last week around 140 members of the elite Kopassus army unit were sent to Wamena to hunt OPM rebels blamed by the military for stealing 29 guns from an armoury.
A subsequent gun fight killed three, including two soldiers.
Army leaders have since indicated that some military personnel may have been involved in the gun theft.