The six men were detained on Sunday after forest rangers in Binh Thuan province stopped their car while they were en route to Ho Chi Minh City and discovered the four dead primates.

A local forest ranger said they were carrying three Phayre's Leaf-monkeys and a Douc Langur monkey as well as a number of weapons and the frozen carcass of a wild boar.

Tran Tien Minh, 49, the owner of the car and two of the rifles, told police he shot two animals himself and bought the others from local people.

Police, however, have determined that all four monkeys were killed by the same type of bullets and believe he killed all of them, the paper said.

The two species of monkeys are listed in Vietnam's "red book", making it a criminal offence punishable by up to seven years in jail for killing them.

The Douc Langur is also listed on the most at-risk Appendix I category under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The Phayre's Leaf-monkey is listed under Appendix II.

The communist nation has an extremely poor record in protecting its wild animals, which are often killed and eaten for their supposed medicinal benefits.

TERRA.WIRE