HANGZHOU - China's first male Olympic swimming champion Sun Yang hit the headlines Monday after he was caught driving without license.

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

Hangzhou police then found the famous swimmer could not provide a driver's license and brought him to the police station for further investigation.

"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 on Monday.

No reports said the top sport star was injured in the accident 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 faces a fine between 200 yuan ($32.79) and 2,000 yuan and up-to-15-day detention.

It was not the first time Sun was in negative exposure. Some media even called his personal life "stained".

"Sun is the leading athlete in Chinese swimming but after the London Olympics, he was in the negative news from time to time," said an article titled "A summary of Sun Yang's stained personal life" on news portal China.com.

It recalled Sun's conflict with his coach Zhu Zhigen and clashes with journalists.

"After a fallout with his coach, Sun was in the news again. Why was him again? This might well be the first reaction when people read about him," commented Chinese portal Sohu on its sports page.

"A question mark is hanging over the public figures -- how should they behave themselves?" it said.

Sun rocketed to join basketball giant Yao Ming and tennis queen Li Na as Chinese sports icons after winning two gold medals at the 2012 London Games, but he went through a difficult year after the Games.

Sun has been struggling to balance his romance and career, which led to strained relationships with his long-time mentor Zhu Zhigen.

Despite gestures of reconciliation in March from both sides, Sun still asked to leave Zhu, with whom he had trained for 10 years, and worked with former Chinese head coach Zhang Yadong.

Sun was crowned with three titles in August's world championships.