China's online censors Thursday scrubbed out a tennis star's reported allegations that a powerful politician sexually assaulted her, the first time that the #MeToo movement has reached the highest echelons of the ruling Communist Party.

Peng Shuai, an ex-world number one doubles player, purportedly made the claim about former vice premier Zhang Gaoli in a post on the Twitter-like Weibo on Tuesday.

Peng reportedly alleged that Zhang, who is now in his seventies, had "forced" her into sex and they had an on-off relationship that lasted several years.

The post appeared to have been deleted quickly and AFP was unable to verify the authenticity of the screenshots containing the allegation, or substantiate the claims made in them.

Weibo data indicated that Peng did post something on Tuesday on her verified account and the post was viewed more than 100,000 times, but the contents are unknown.

There was no further word from the 35-year-old Peng and also no public response from Zhang, a former member of China's powerful seven-member Politburo Standing Committee and reportedly close to Premier Li Keqiang.

Chinese censors have since blocked all mention of the claims apparently made by Peng, a former Wimbledon and French Open doubles champion.

Searches on China's tightly controlled Internet, including on Weibo and the Baidu search engine, also show no results when Peng and Zhang's names are entered together.

Peng's Weibo account was still up on Thursday, but does not show up in search results on the platform.

In the apparent screenshots of Peng's lengthy and heartfelt post accusing Zhang of pressuring her into sex, she purportedly wrote: "I was very scared.

Peng Shuai is a prominent Chinese tennis player who was number one in doubles
Peng Shuai is a prominent Chinese tennis player who was number one in doubles AFP / GREG WOOD

"I initially refused and kept crying."

Peng reportedly claimed they went on to have a relationship that continued until Zhang stopped recently contacting her.

She had no evidence of the claimed relationship, she said, but added that Zhang's wife knew of it.

The experience left her with self-loathing, she is said to have written.

"Even if it is no more than throwing an egg against a rock, I -- courting disaster like a moth attracted to a flame -- will speak the facts about what happened," Peng allegedly wrote.

China saw a fledgling #MeToo movement emerge in 2018, with allegations involving powerful public figures.

But such claims against top political leaders have not been made publicly until now.

"Peng Shuai speaking up shows that #MeToo will not be stopped," said Zhou Xiaoxuan, who in 2018 accused a prominent television host of sexual harassment.

"As long as there is sexual assault taking place under unbalanced power structures, there will be women who experience pain... and speak up," she added.

Feminist activist Lu Pin told AFP that Peng's accusations were "very important" as they pointed to an unseen side of top Chinese officials.

"Peng Shuai's self-report is that of yet another imperfect victim," Lu said on Twitter.

"It is very difficult to break through the unspeakability and normalisation of sexual violence set by an entire society with the meagre power of an individual."