The Indonesian military has arrested three soldiers on suspicion of kidnapping, torturing and killing a civilian in an extortion plot, officials said Tuesday.

According to the military, the victim was tortured to death, and local media reported that his body was later found in a river in the West Java town of Karawang.

The victim’s relatives identified him as 25-year-old Imam Masykur, according to local media reports.

The family said the soldiers tried to extort him for 50 million rupiah ($3,278) before he was killed.

“This case involved three soldiers from the units of the Presidential Security Regiment (Paspampres) and the Army,” Brigadier General Hamim Tohari, Indonesia’s army spokesperson, told a press conference Tuesday.

“What is certain is that it started with kidnapping, extortion and assault that led to a fatality.”

Rights groups have long criticised Indonesia’s army for alleged abuses of civilians and for failing to reform its opaque military justice system.

The case against the three soldiers has shocked the nation and was splashed across main television channels on Tuesday.

Tohari said the case was reported to Jakarta’s metro police on August 14 before it was transferred to military police when the three soldiers became suspects, meaning they face trial in a military court.

One civilian was also arrested on suspicion of involvement.

Rights advocates said the trial should take place in a criminal court, however, as the victim was a civilian.

“Security personnel suspected of involvement in torture and other inhumane acts should not only face internal sanctions but also legal proceedings in a public court according to principles of fair justice,” Amnesty International Indonesia director Usman Hamid told AFP.

“We urge for the perpetrators to be brought within the realm of public jurisdiction, to be tried by judges of integrity, and to be given appropriate punishment.”

NGOs have alleged that military tribunals, often held behind closed doors, have been used to shield human rights violators from transparent proceedings.