Ryan Murphy lost the second of his Rio backstroke titles to Russian Evgeny Rylov at the 2020 Olympics on Friday and the U.S. swimmer then suggested doping had played a part in his demise as events took an acrimonious turn at the Tokyo pool.

The celebratory mood after another morning of memorable racing at Tokyo Aquatics Centre changed after Murphy relinquished the 200-meter backstroke crown, as Rylov, who also won the 100, touched first in an Olympic record.

"It is a huge mental drain on me to go throughout the year, that I am swimming in a race that's probably not clean and that is what it is," Murphy told a reporter in the post-race "mixed zone" after finishing second to the Russian with Britain's Luke Greenbank taking bronze.

But at a later news conference the American, who took bronze in the 100m, backed away from any suggestion that his rivals in the race had cheated.

"I need to be clear, I've never made ... , my intention is not to make any allegations here. Like, congratulations to Luke and Evgeny. They did an incredible job, they're both very talented swimmers," he said.

"At the end of the day ... I do believe it (doping) is still big in swimming and it is what it is."

Instead of reliving his thrilling victory at his post-race news conference Rylov found himself defending his doping record.

"I always do the doping tests ... I would not be able to forgive myself if I had taken something. I don’t know how to react to this. I haven’t been accused of anything," he said.