China on Tuesday said the controversy surrounding Peng Shuai was being "maliciously" hyped up, after the Chinese tennis star made sexual assault claims against one of the nation's most powerful politicians.

Peng, a Wimbledon and French Open doubles champion, was not seen for more than two weeks after she made the accusations against former vice-premier Zhang Gaoli.

The 35-year-old Peng reappeared in public for the first time at the weekend when she was seen attending a Beijing tennis tournament.

"I think some people should stop deliberately and maliciously hyping up, let alone politicise this issue," said foreign ministry spokesman Zhao Lijian in response to a question on whether the case affected China's international image.

Beijing will host the Winter Olympics in February.

"I believe you have all seen that she recently attended some public events and had a video call with IOC president Thomas Bach," Zhao added.

The comment was the most direct response from the Chinese government to Peng's case.

Until Tuesday, Beijing had repeatedly brushed off questions about her whereabouts and welfare -- calling them "not a diplomatic issue".

Evidence of her claims have also been scrubbed from China’s highly censored Internet.

The Women's Tennis Association (WTA) has threatened to end lucrative contracts with China unless it gets word of Peng's safety.

- IOC call & criticism -

Peng appeared in a 30-minute video call with the International Olympic Committee (IOC) chief on Sunday.

The organisation said in a statement that during the call, "Peng Shuai thanked the IOC for its concern about her well-being."

"She explained that she is safe and well, living at her home in Beijing, but would like to have her privacy respected at this time," it said.

Earlier Sunday, Peng was seen attending a Beijing tennis tournament, in official photos of the event.

But human rights groups and sporting authorities overseas have continued to voice concern about Peng and whether local authorities will act on her allegations.

"This video does not change our call for a full, fair and transparent investigation, without censorship, into her allegation of sexual assault, which is the issue that gave rise to our initial concern," the WTA said, when asked about the IOC call.

Human Rights Watch also slammed the IOC and called for them to explain how the video call with Peng had been organised.

"The IOC has vaulted itself from silence about Beijing’s abysmal human rights record to active collaboration with Chinese authorities in undermining freedom of speech and disregarding alleged sexual assault," said Yaqiu Wang, senior China researcher at Human Rights Watch.

"The IOC appears to prize its relationship with a major human rights violator over the rights and safety of Olympic athletes."

Peng, a two-time Grand Slam doubles champion, alleged earlier this month that Zhang, now in his 70s, "forced" her into sex during an on-off relationship spanning several years.

Following a global outcry, including from tennis superstars and the United Nations, Chinese state media reporters have released a flurry of footage purporting to show all is well with Peng.

Peng's claims against Zhang were the first time China's #MeToo movement has touched the highest echelons of the ruling Communist Party.