American swimmer Ryan Murphy says he can't know for sure if 200m backstroke winner Evgeny Rylov of the Russian Olympic Committee team doesn't use performance-enhancing substances.

TOKYO -- American swimmer Lilly King doubled down on criticism of Russian athletes hours after the president of the Russian Olympic Committee said his teams' medals are the "best answer" to critics who questioned why the country is allowed to compete following doping scandals.

Her comments came hours after ROC president Stanislav Pozdnyakov said critics "supposed that as a matter of fact our athletes can't compete without doping," but that Russian athletes in Tokyo "proved the opposite not just with words but with their deeds and results.".

Murphy bemoaned Friday that his races were "probably not clean" after taking the silver medal behind Russian swimmer Evgeny Rylov in the 200-meter backstroke.