A three-year-old female polar bear kept in a shopping mall aquarium in southeastern China, at the centre of an animal rights controversy, is showing signs of mental decline, animal welfare groups said.

The bear, named Pizza, attracted the attention of international news media after Hong Kong-based Animals Asia posted a video on its website in July that showed visitors at the Guangzhou mall taking photos of her as she lay on her side in the blue enclosure.

The group called Pizza "the tragic bear that suffers for selfies."

Humane Society International (HSI) on Tuesday released a video of Pizza, which it said showed "worrying stereotypical behaviours such as head swaying and repetitive pacing, evidence of frustration and mental decline."

The group and three Chinese animal rights groups held a press conference on Tuesday calling for the closure of the aquarium at Grandview Mall.

Yu Hongmei, founder of Dalian-based VShine Animal Protection Association, said at the press conference on Tuesday that "a shopping mall is not the place to exhibit animals."

Activists say Pizza, a polar bear on display at the Grandview Aquarium in a shopping mall in Guangzhou, China, is showing signs of mental decline. (Reuters)

The Telegraph, Time and other global media outlets have also called Pizza "the world's saddest polar bear."

In an email reply to Reuters on Wednesday, Grandview Mall Aquarium said they disagreed with the animal rights groups' reports on Pizza's condition.

They released their own video that showed Pizza swimming in its aquarium and getting fed by staff. Grandview said that Pizza's tank, at 150 square metres, complies with Chinese regulations for such enclosures.