The last polar bear kept in South Korea has died of old age only weeks before his planned departure to better living conditions in Britain, zoo officials said Thursday.

Tongki -- a 23-year-old male named after a Japanese cartoon character of the 1980s -- lived in a 330-square-metre (3,500-square-foot) concrete enclosure at the Everland theme park outside Seoul.

The zoo had planned to move him to the Yorkshire Wildlife Park next month to allow him to enjoy his final days in more appropriate surroundings -- the facility in northern England has a 40,000 square metre polar reserve -- and had thrown him a farewell party in June.

But Tongki was found dead on Wednesday night and autopsy results suggested that he appeared to have died of old age, the zoo said in a statement, adding it plans to conduct more tests to determine the exact reason for his death.

The average life span of polar bears is around 25 years and Tongki was the equivalent of around 80 in human terms.

"We have designated this week as a period of mourning for Tongki and decorated his living space so visitors can say farewell," a zoo official told AFP.

Born in captivity at a zoo in the southern city of Masan, Tongki was the only polar bear still living in South Korea and had been alone at Everland since the last fellow resident of his species died three years ago.

Everland said Tongki will not be replaced, and other South Korean zoos have no plans to import the animals, which are classed as "vulnerable" on the International Union for Conservation of Nature's Red List of endangered species.

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