Teenage gymnast Shoko Miyata has been pulled from Japan's team for the Paris Olympics after being caught smoking and drinking, officials said on Friday.

The 19-year-old, a world bronze medallist and captain of Japan's women's gymnastics team for the Games, was sent home from their training camp in Monaco after admitting she had violated their code of conduct.

"With her confirmation and after discussions on all sides, it has been decided that she will withdraw from the Olympics," Japan Gymnastics Association (JGA) secretary general Kenji Nishimura told reporters in Tokyo.

Nishimura said the association had been told that Miyata was seen smoking in a private setting in Tokyo some time at the end of June or beginning of July.

She also reportedly drank alcohol in a room at Japan's national training centre.

Smoking and drinking are both illegal under the age of 20 in Japan.

Nishimura said it was not clear whether Miyata was at a party or drinking alone.

"Being a member of the Japan national gymnastics team is a position where you have high demands on you all the time," said JGA chairman Tadashi Fujita.

Fujita said that Miyata was already back in Japan after leaving the team's camp and that the JGA would give her support.

Miyata won bronze in the balance beam at the 2022 world championships in Liverpool.

She won the all-around title at Japan's national championships earlier this year. (AFP)