HANGZHOU -- China's first male Olympic swimming champion Sun Yang was driving without license when his Porsche SUV collided with a bus, police said.

No reports said the top sport star was injured in the accident on Sunday afternoon in Hangzhou and the 21-year-old apologized for his behavior on Monday.

"I should have been a role model as an athlete and a public figure but I failed my responsibility," said Sun.

"I am deeply sorry for what I have done and will reflect on my behavior. Because I have been focusing on training and competition, I ignored learning some legal knowledge, which led to my mistake," he wrote on Weibo, the Chinese microblogging equivalent to Twitter.

Sun was driving luxury SUV Porsche Cayenne he claimed was borrowed from a relative when a bus hit his car from the back.

Hangzhou police then found the famous swimmer could not provide a driver's license.

"After looking into the system, we did not find any record of his license. Sun admitted he did not have one," Hangzhou police told Xinhua.

Sun faces a fine between 200 and 2,000 yuan and up-to-15-day detention.