"When I was working at Pinduoduo, I started working at 11 a.m. and usually finished at 11 p.m. or 12 p.m., six days a week," the employee, who gave his surname as Wang, told Xinhua.

Pinduoduo did not immediately respond to a request for comment on the report. It earlier confirmed that a female employee collapsed while walking home from work with a colleague on December 29 and later died in hospital. The cause of her death was not disclosed.

Pinduoduo is one of China's internet giants, a sector under fire by the authorities and facing new rules aimed at reining them in.

The labour protection department of the district in Shanghai where Pinduoduo is headquartered is looking into the company's working hours and employment contracts, the Beijing Youth Daily reported last week.

"Anti-trust is the big background," said Liu Wanyong, former senior editor at China Youth Daily. "So the Chinese media attack big internet firms that they believe to be 'monopolistic' because it's the politically correct thing to do."

Wang came to the attention of Chinese social media watchers after he released a video in which he described long working hours and said he had been fired for posting a photo of a Pinduoduo employee being carried away in an ambulance.

The company told Reuters it had fired Wang because he had previously made a series of "malicious" comments about Pinduoduo on social media.

The Xinhua report was read 1.29 million times on Wednesday, and topics mentioning Pinduoduo and its company culture have been among the top trending ones on China's Twitter-like Weibo over the past week.

Wang did not respond to a Reuters request for comment.

(Reporting by Sophie Yu and Brenda Goh; editing by Jason Neely)