The United States and UN on Friday demanded proof of Peng Shuai's whereabouts as concern rises for the tennis star, who has not been seen in public since alleging she was sexually exploited by a former vice-premier of China.
Late Friday photos of a smiling Peng emerged on a Chinese state media-affiliated social media account, but their authenticity could not be verified and the user did not respond to AFP's request for comment.
Earlier White House press secretary Jen Psaki had said President Joe Biden's administration wanted China to "provide independent, verifiable proof" of Peng's whereabouts and expressed "deep concern" about the former world top-ranked doubles player.
The United Nations insisted on a fully transparent investigation into the claims made by Peng against Communist Party grandee Zhang Gaoli -- the first time China's #MeToo movement has touched the highest echelons of the country's politics.
Peng, 35, alleged on the Chinese social media site Weibo earlier this month that Zhang, now in his 70s, had "forced" her into sex during a long-term on-off relationship.
The claims were quickly scrubbed from the Twitter-like platform and Peng has not been seen publicly since.
"It would be important to have proof of her whereabouts and well-being," Liz Throssell, a spokeswoman for the UN Human Rights Office, told reporters in Geneva.
"We are calling for an investigation with full transparency into her allegation of sexual assault."
Other tennis stars, sports bodies, governments and human rights defenders have added to the growing clamor for information.
China has repeatedly refused to comment on the case.