A rare public accusation of sexual assault aimed at a retired senior Chinese official has rocketed around China’s internet and turned a spotlight on perceived abuses by powerful political figures.

Peng Shuai, a professional tennis star, accused Zhang Gaoli, who served as vice premier from 2013 to 2018, of sexual assault in a post Tuesday night on her verified account on China’s Twitter-like Weibo platform, where she has more than half a million followers.

In...

A rare public accusation of sexual assault aimed at a retired senior Chinese official has rocketed around China’s internet and turned a spotlight on perceived abuses by powerful political figures.

Peng Shuai, a professional tennis star, accused Zhang Gaoli, who served as vice premier from 2013 to 2018, of sexual assault in a post Tuesday night on her verified account on China’s Twitter-like Weibo platform, where she has more than half a million followers.

In the post, which disappeared after roughly 20 minutes, Ms. Peng, 35 years old, described an on-and-off relationship with Mr. Zhang lasting for some years that she said was sometimes consensual and sometimes involved coercion, including forced sex. Efforts to reach Ms. Peng or representatives of hers weren’t successful.

Peng Shuai, 35 years old, is one of China’s top tennis players.

Photo: Bai Xue/Xinhua/Zuma Press

Ms. Peng’s post, a screenshot of which was seen by The Wall Street Journal, marks perhaps the most public accusation leveled directly at such a high-level official during the Communist Party’s time in power and comes ahead of a closely watched leadership reshuffle next year.

“I know that for someone of your seniority, Vice Premier Zhang Gaoli, you’ve said that you’re not afraid. But even if I’m like an egg striking a stone, or a moth darting into the flames, inviting self-destruction, I’ll tell the truth about you,” Ms. Peng wrote in her post.

Ms. Peng, who was ranked No. 1 in women’s doubles with the Women’s Tennis Association in 2014, said that she would be unable to offer evidence to support her accusation. She said Mr. Zhang had first assaulted her after inviting her to play tennis with him and his wife. She didn’t give details or specify when exactly that occurred but said that she had maintained a relationship with Mr. Zhang beginning about 10 years ago.

The State Council, China’s cabinet, didn’t immediately respond to a request for comment. Mr. Zhang couldn’t be reached for comment.

Mr. Zhang, shown in 2017 in Beijing, is seen as a low-key official in the Communist Party despite his leadership experience in China’s economically advanced regions.

Photo: wang zhao/Agence France-Presse/Getty Images

Mr. Zhang, who was born in November 1946, advanced his political career mainly in the southern province of Guangdong, where he served for more than a decade. He is widely regarded as a low-key official in China’s ruling Communist Party despite his leadership experience in the country’s more economically advanced regions, including the showcase city of Shenzhen in Guangdong and the large manufacturing base of Shandong Province.

People’s Daily, the Communist Party’s main mouthpiece, reported that Mr. Zhang enjoys playing tennis in an article published in 2013, when he became vice premier.

Ms. Peng is one of China’s top tennis players. She won a women’s doubles title at Wimbledon in 2013 and another at the French Open in 2014. She also reached a career-high singles ranking of 14th in the world in 2011.

Her Weibo post accusing Mr. Zhang of sexual assault caused a stir online, even after it was removed from China’s internet, with many people commenting that they saw it as proof that powerful political figures in the country use their positions to procure sexual favors.

Searches for “Peng Shuai” on popular Chinese social-media platforms such as Weibo and the Quora-like platform Zhihu were blocked. When asked about Ms. Peng’s allegation during a regular press conference Wednesday, a Chinese foreign ministry spokesman, Wang Wenbin, said he hadn’t heard of it.

Ms. Peng, shown playing at the Australian Open in Melbourne last year, said in her post Tuesday that she couldn’t provide evidence for her allegation but vowed to ‘tell the truth’ despite personal risk.

Photo: Andy Brownbill/Associated Press

While a public accusation against a political leader as senior as Mr. Zhang has few if any precedents, the party has a tradition of disclosing the sexual misconduct of already disgraced top officials and executives at state-run companies.

Notably, official accounts marking the downfall of disgraced former official Zhou Yongkang—like Mr. Zhang, a former Politburo Standing Committee member—included allegations of sexual impropriety when he was convicted of corruption-related charges in 2014. State media also reported that Lai Xiaomin, chairman of China Huarong Asset Management Co. from 2012 to 2018 when he was fired for graft, had more than 100 mistresses. Neither Messrs. Zhou nor Lai has responded to those allegations.

Ms. Peng’s allegations against Mr. Zhang come as China’s leadership enters a delicate period in its political calendar ahead of a Communist Party congress slated for late next year. During that gathering, the party is expected to replace retiring central leaders with new ones, while leader Xi Jinping is expected to secure a third term of five years.

Mr. Xi and other senior officials are set to review a draft resolution next week that lays out an official accounting of the party’s “major achievements and historical experiences” since its founding 100 years ago.

The resolution would be the third such document approved by the party, putting Mr. Xi on a par with Mao Zedong

and Deng Xiaoping as leaders who commanded the preponderant authority needed to formally reinterpret modern Chinese history.

Correction
Peng Shuai’s surname is Peng. It was incorrectly given as Shuai in a photo caption in an earlier version of this article. (Corrected on Nov. 4)