The four include three pig-tailed monkeys and one rhesus. They were handed over by residents from the districts of Ky Anh, Lac Son and Loc Ha on September 21.
Two among the four monkeys handed over to Vu Quang National Park
The move followed calls by local authorities to improve awareness about the need to protect wild animals.
The animals will be released back into the wild.
In March this year, fifty-six animals were also released into Vu Quang National Park, mostly pig-tailed monkeys and big-headed turtles.
The monkeys are listed as rare and endangered animals that need to be preserved.