A global campaign to free the world's "saddest polar bear" from a Chinese shopping centre has gathered one million signatures, rights groups said, as a new video of the wretched-looking creature sparked fresh outrage.

The bear named Pizza is one of 500 species kept in a zoo inside the mall in the southern Chinese city of Guangzhou and activists have been lobbying for the animals to be rehomed and the exhibition closed.

Letters signed by 50 Chinese animal rights groups were sent to the governor of Guangdong province and the shopping centre this week calling for the zoo's closure on the grounds it is illegal.

Animals, including an arctic fox, wolf and walrus, are kept in "small rooms with no window and environmental enrichment", said a copy of the letter sent to Governor Zhu Xiaodan and seen by AFP.

"Such conditions are far from their natural habitat and would cause inevitable harm to their mental and physical health."

Two petitions that had gathered a total of one million signatures from around the world were also sent to Zhu.

Qin Xiaona, director of the Beijing-based Capital Animal Welfare Association and one of the signatories of the letters, told AFP on Friday they were still waiting for a response.

The general manager of the atraction, a man surnamed Fan, declined to immediately comment when AFP contacted him by telephone on Friday.

Fan said previously that the zoo was "legally compliant" but pledged to "strengthen the protection of animal rights and welfare".

But a video released by Humane Society International this week shows Pizza pacing around his glass-fronted enclosure measuring 40 square metres (430 square feet) and shaking his head as onlookers take photos on their cell phones.

At one point the forlorn-looking bear lies on the floor in front of an air vent, which HSI director of international media Wendy Higgins told AFP suggested he was trying to get a "rush of fresh air".

Pizza's behaviour -- head swaying and repetitive pacing -- had been induced by "frustration and poor welfare", Professor Alastair Macmillan, a veterinary adviser to HSI, said after viewing the footage.

"The conditions in which he is being kept are completely unsuitable, vastly removed from anything approaching his natural habitat, and if something is not done then he will likely slip further and further into mental decline," Macmillan said in a statement.

An earlier offer from the Yorkshire Wildlife Park in England to adopt Pizza on the condition that he was not replaced by another polar bear was not taken up by the shopping mall, which said it had "no need" for foreign interference.

Higgins said the Grandview zoo was part of a trend among Chinese retailers to use animals to entice customers back to bricks-and-mortar stores instead of shopping online.

"Over the past decade there has been a huge campaign to build mega malls in China but the success of e-commerce in the country has seen a drop off in shoppers going to them," she said.