Sun Yang speaks to media at the final of the men's 800-meter freestyle event during the swimming competition at the 2019 World Champion-ships in Gwangju, South Korea on Wednesday. Sun finished sixth in the final. Photo: VCG

Chinese swimmer Sun Yang said he will "definitely" appeal the ruling of an eight-year ban issued on him by the Court of Arbitration for Sport, as the Chinese Swimming Association said it will continue to support the athlete's legal rights.

"This is unfair. I firmly believe in my innocence," Sun told the Xinhua News Agency. "I will definitely appeal to let more people know the truth."

The Court of Arbitration for Sport (CAS) on Friday slapped an eight-year ban on China's swimming star Sun over a doping test in September 2018.

"The athlete [Sun] failed to establish that he had a compelling justification to destroy his sample collection containers and forego the doping control," the CAS ruling said. 

The Chinese Swimming Association expressed "deeply regret" over the ruling.

Sun, a three-time Olympic gold medalist, is able to appeal the ruling to the Swiss Federal Tribunal within 30 days.

A vial of Sun's blood sample was smashed with a hammer during a testing session in September 2018, but Sun was acquitted by swimming's governing body FINA after Sun challenged the credentials of the doping control officers. 

But it outraged the World Anti-Doping Agency (WADA), which later took the case to CAS. 

"It is one thing to provide a blood sample and to question the accreditation of the testing personnel while keeping the intact samples in the possession of the testing authorities," the CAS statement said. 

"It is quite another thing, after lengthy exchanges and warnings as to the consequences, to act in such a way that results in destroying the sample."

Sun, also the 1,500-meter freestyle world record holder, was training behind closed doors in Beijing as he prepares for the Tokyo Olympics. 

"The results achieved by the athlete in the period prior to the CAS decision being issued should not be revoked," the CAS statement said. 

But the verdict is likely to deal a blow to China's swimming team, as Sun remains a medal favorite in the men's 200- and 400-meter freestyle in the 2020 Olympics in Tokyo.