Three Indonesians and a Malaysian went on trial Tuesday for killing endangered orangutans and other protected primates as a means of pest control at a palm oil plantation on Borneo island.

Prosecutors said the plantation manager, Malaysian national Phuah Chuan Hun, and his employee Widiantoro paid two men between 2009 and 2010 to kill the primates.

The plantation employees and the two killers, Imam Muhtarom and Mujianto, were charged with killing endangered species and all face five years in jail.

"The two men were paid one million rupiah ($111) for each orangutan and 200,000 rupiah ($22) for other monkeys," prosecutor Suroto told the Tenggarong district court.

The plantation, in East Kalimantan province on Indonesian Borneo, is a subsidiary of the publicly listed Malaysian-owned Metro Kajang Holdings.

"The two used a 4.5-millimetre calibre airsoft gun to shoot the orangutans out of trees before their six hunting dogs chased them," Suroto said.

They would then hit the orangutans afterwards with rocks or wooden sticks before tying them up with rope to take photographs as evidence, he said.

Police arrested the four men in November after photos of them with their prey, including long-nosed monkeys found only on Borneo, circulated around the community.

The men were charged with killing one baby and two adult orangutans, but police said earlier that at least 20 had been killed based on receipts of from the company amounting to 25 million rupiah ($2,775).

Experts say there are about 50,000 to 60,000 orangutans left in the wild, 80 percent of them in Indonesia and the rest in Malaysia.

They are faced with extinction from poaching and the rapid destruction of their forest habitat, driven largely by palm oil and paper plantations.

The trial will resume next week.