Tran Van Toan was carrying the tranquilized bear in his taxi on National Route 1A near Can Loc District at around 7 p.m. when police flagged down the vehicle on suspicion.

They found the bear in a cage in the back, and Toan had no documents indicating why he was transporting the animal.

He told the officers he had been asked by an acquaintance to carry passengers from Can Loc to the neighboring province of Nghe An, but upon reaching the pick-up destination the acquaintance told him to transport the bear.

"I initially declined, but they said the bear has all the necessary documents and they would take all responsibility. I agreed for a little extra cash."

The bear was handed over to a wildlife preservation center in the northern Ninh Binh Province.

The police are continuing their investigation.

Vietnam is home to both the moon bear and the sun bear, species listed as vulnerable by the International Union for the Conservation of Nature.

Violation of wildlife protection laws is punishable by up to seven years in jail.

There are around 450 captive bears in the country, mostly moon bears, on 150 private farms. They had been kept to extract bile, which is used to treat various ailments, according to Four Paws Vietnam Foundation.

Although commercial bear bile extraction was banned in 2005, farms already having bears were allowed to keep them.