RIO DE JANEIRO (AFP) - American teenager Lilly King celebrated her victory over tainted Russian swimmer Yulia Efimova in the women's 100m breaststroke final by firing yet another anti-doping salvo against the Russian.

Hostilities escalated between swimming stars from various nations in Rio as King, 19, was joined by Michael Phelps and other swimmers in calling for tougher action on the use of banned substances.

Efimova, who was initially disqualified from competing in Rio by international swimming body Fina, was cleared to take part on the basis of an appeal to the Court of Arbitration for Sport on the eve of the opening ceremony.

The Russian served a 16-month suspension from late 2013 to February 2015 and also failed a test for meldonium earlier this year, although the result was later overturned.

Efimova, 24, was booed by spectators as she entered the pool area before the final and was left in tears after being narrowly beaten by King.

"I think it just proved that you can compete clean and still come out on top," King said of her win.

The Russian, who had refused to speak to reporters after her semi-final swim, broke down when she faced journalists after finishing second in the final. "I once made a mistake and served my ban," she said, referring to her 16-month suspension.

"The second time was not my mistake. I don't know how to make people understand. If yogurt gets banned and you're positive, is that your fault?"

US competitors in Rio have been outspoken about their Russian rivals. Phelps, who is aiming for a record 20th gold medal on Tuesday (Brazil time), backed King and said those punished for doping should not be allowed back in the sport.

"I think you're going to see a lot of people speaking up more," he said. "I think she's right, something needs to be done."

Also at the centre of the doping controversy in Rio is China's Sun Yang, who won the men's 200m freestyle gold on Monday.

Sun has already been involved in a verbal battle with Australia's Mack Horton, who beat him in the 400m freestyle final. After his victory in the 200m freestyle title, the Chinese swimmer, who was banned for three months in 2014, also came under attack from French swimmer Camille Lacourt, who finished fifth in the 100m backstroke.

"Sun Yang, he p***** purple," Lacourt told French radio after his race. "When I see the 200m podium I want to be sick.

"I am very sad when I see my sport getting like this. I have the impression I am watching athletics, with two or three doped in each final."