JINAN, May 15 -- Netizens' accusations of misuse of power seem to have prompted police in east China's Shandong Province to apologize for detaining a man who had gone online to vent his fury at the parking ticket they had given him.

Traffic police in Yanzhou City wrote out a ticket on April 28 and posted it on a car illegally parked by the roadside. In response, the car owner, surnamed Cao, posted "Yanzhou police really suck!" on a local Internet forum.

In a statement posted on Tuesday on its official account with microblogging service Sina Weibo, the Public Security Bureau of Yanzhou said that Cao had "publicly insulted the police of the people and produced a very bad impact on the society," and consequently had been put into custody for five days as punishment.

At the end of the statement, police warned the public that any words and comments on the Internet, even under a pseudonym, could be traced, and that anyone who breaks the law must be brought to justice.

The post instantly went viral, incurring a spate of comments, most of which questioned the legitimacy of such punishment.

Internet user "Xiaruolixia" said the law is designed to safeguard justice rather than to protect the police themselves. Cursing police online is only a problem of personal ethics and should not be dealt with by law enforcement, according to the netizen.

The post was removed shortly after.

Late on Wednesday, Yanzhou police put up another post on Sina Weibo, saying Cao's detention was improper and that they had decided to withdraw the punishment and apologize to him. In the meantime, officers involved in the case would be taken to account.

Liu Min, a lawyer with Beijing-based Yingke Law Firm, said it was baseless in legal terms to detain Cao over his verbal misconduct. "It is misuse of power by authorities," Liu said.

However, the lawyer noted that Cao's written attack on the police went beyond freedom of speech.

Xia Xueluan, a sociologist at Peking University, said cyber-violence is intensifying in China as many people prefer to vent their grievances online. He said the case has rung alarm bells for Internet users and reminded them of the need to behave properly and abide by the law.

Another lawyer, Hao Jiyong, said Cao could have lodged his complaints through petition. "But the public security authorities also need to handle such complaints with more flexibility rather than resort to detention at will."