Image copyright other Image caption The monkeys were endangered grey-shanked douc langurs

Vietnamese authorities have detained three soldiers suspected of torturing and killing two rare monkeys, state-run Voice of Vietnam newspaper reports.

One of the men had posted photos on Facebook showing how the monkeys were killed, triggering a public outcry.

The monkeys were endangered grey-shanked douc langurs (Pygathrix cinerea), reports say.

The soldiers, stationed in Vietnam's Central Highlands area, are now under investigation.

One of them, Nguyen Van Quang, who is serving in the Tay Nguyen Command of the Vietnamese army, posted photos of the monkeys on his Facebook page last week.

The photos showed one of the monkeys, believed to be pregnant, being made to smoke a cigarette before it was tortured and killed.

Col Nguyen Van Hai, head of Tay Nguyen Command's Military Prosecutor's Office, told the Voice of Vietnam that the soldiers had been detained and were being questioned.

"We're still continuing our investigation into the case. When we have enough evidence, they [the soldiers] will be dealt with in accordance with Vietnamese military laws," he said.

He added that the three had admitted killing the monkeys and said they had bought them from locals.

The men, who were identified on Thursday, are set to appear in a military court on an as yet unspecified date.

What is more worrying about the incident is that the young soldier who posted the photos on Facebook did not think he did anything wrong, says Nga Pham from BBC Vietnamese.

Authorities now realise that they need to do something to educate people, especially the young, about animal welfare and protection, she adds.