Hong Kong police said on Sunday they had arrested a 21-year-old man after he reportedly said on social networking site Facebook that he would hack several government websites.
Police said the man, who was later released on bail, was held on suspicion of "access to a computer with criminal or dishonest intent" after he allegedly threatened to hack seven government websites between June and August this year.
"The Internet is not a virtual world of lawlessness," a police spokesman said, adding that the man was required to report back to the police in October.
The unidentified man was arrested on Friday before being released on bail, the spokesman told AFP.
He faces up to five years imprisonment if found guilty.
The man is a member of the global hacker group Anonymous, the South China Morning Post said. The group is said to have 20 members in the semi-autonomous Chinese territory, which guarantees civil liberties not seen on the mainland, including freedom of speech.
The police spokesman declined to confirm his link to Anonymous. The last posting on the "Anonymous HK" Facebook page on July 22 urged authorities to show "respect" to citizens.
The notorious group, which is believed to be a loosely affiliated network of "hacktivists", has attacked sites of groups as varied as MasterCard and Visa, the US Justice Department, and the Tunisian and Yemen governments.