South Korea's double Olympic short-track gold medalist Shim Suk-hee has accused her former coach - already convicted and jailed for repeatedly beating her over many years - of sexual assault, her lawyer said Wednesday.

Shim filed her complaint against Cho Jae-beom to police last month, on the same day she testified at his appeal against a 10-month jail sentence for physically assaulting her.

Aged 21, the elite athlete has four Olympic medals to her name, including relay golds at both Sochi 2014 and on home ice at last year's Pyeongchang Games.

Shim told police that her coach sexually violated her from the age of 17 until January 2018, a month before the Olympics, her lawyer said.

"This is a grave crime that our society should not overlook," Im Sang-hyeok told AFP.

Some of the incidents took place at government-managed sports training centers, the lawyer added, demonstrating how vulnerable sports players can be to loopholes in the state management system.

South Korea is a regional sporting power and regularly in the top 10 medal table places at the summer and winter Olympics.

But in an already intensely competitive society, winning is everything in its sports community - where coaches hold immense sway over athletes' careers, and physical and verbal abuse are known to be rife. 

In addition, the country remains ­socially conservative and female sex crime victims can face public shaming.

Shim "kept it all to herself" until recently, lawyer Im said of the sexual assault allegations, "in fear of the potential stigma she could face as a woman and impact on her family as well as reprisals by Cho."

She "mustered up the courage" to reveal the case in hope of preventing other athletes suffering similar fates, he added.