The head of the Women's Tennis Association (WTA) has cast doubt on an email released by Chinese state media attributed to tennis player Peng Shuai.

Steve Simon, chairman of the WTA, said in a statement he had a "hard time believing" the email was written by Ms Peng or on her behalf.

One of China's biggest sporting stars, she has not been heard from since she made sexual assault allegations against a top Chinese official.

The email was shared on Wednesday.

Broadcaster CGTN published the correspondence - allegedly written by Ms Peng - online. Written in her voice, it claims she was not missing or unsafe, adding: "I've just been resting at home and everything is fine."

The email also said the sexual assault allegation attributed to her was false.

Many responding on social media have cast doubt on the authenticity of the email - including pointing out that a typing cursor appears to be visible on the screenshot of the email published by CGTN.

Ms Peng - a former number one-ranked tennis doubles player - had not been heard from since posting an allegation about former Vice Premier Zhang Gaoli on Chinese social media site Weibo in early November.

She alleged she was "forced" into sexual relations with Mr Zhang - who served as the country's Vice Premier between 2013 and 2018 and was a close ally of China's leader Xi Jinping - in a post that was later taken down. She has not been seen or heard from publicly since.

The WTA and leading voices from the world of tennis have increasingly spoken out about Ms Peng since.

Earlier this week, world number one male tennis player Novak Djokovic said he hoped she would okay, adding that he was shocked, while Naomi Osaka voiced concerns about Ms Peng's whereabouts.

Responding to the email published Wednesday, WTA chair Steve Simon said the email he received "only raises my concerns as to her safety and whereabouts".

"I have a hard time believing that Peng Shuai actually wrote the email we received or believes what is being attributed to her," he said in a statement, adding: "The WTA and the rest of the world need independent and verifiable proof that she is safe."

Mr Simon also reiterated that her sexual assault allegation must be investigated "with full transparency and without censorship".

"The voices of women need to be heard and respected, not censored nor dictated to," he added.

Ms Peng, 35, is a prominent figure in Chinese tennis. She has won two Grand Slams at Wimbledon in 2013 and the 2014 French Open, both alongside Taiwan's Hsieh Su-wei.

Her allegation is the highest profile incident in China's fledgling #MeToo movement. It comes just months before China hosts the Winter Olympics. (BBC)