BEIJING — The Chinese government, reversing a 25-year ban, announced on Monday that it would allow the use of rhinoceros horns and tiger bones in medicine, a move that environmentalists described as a significant setback for efforts to protect the animals from extinction.

The State Council, China’s cabinet, said in a policy directive that it would legalize the use of rhino horns and tiger bones for “medical research or in healing,” but only by certified hospitals and doctors, and only from rhinos and tigers raised in captivity, excluding zoo animals. While such remedies are highly profitable, they have no proven benefits to humans.

Environmentalists said the decision would likely help fuel a black market for wild rhino and tiger parts, which are revered in traditional Chinese medicine for supposed healing powers, and could lead to increased poaching of the fewer than 30,000 rhinos and 3,900 tigers still in the wild.