BEIJING (AFP) - A controversial nationalist professor in China has had his microblog account suspended after he posted a comment about the 1989 Tiananmen Square protests, in which he took part as a student.

Kong Qingdong, a professor at the elite Peking University who claims to be descended from the ancient sage Confucius, is well-known in China for his outspoken comments, including a tirade in which he condemned residents of Hong Kong as "bastards" and "dogs".

But a remark on the popular Sina Weibo microblogging service - where he had around 2.75 million followers - seems to have crossed the line with Communist authorities wary of any discussion of the bloody Tiananmen crackdown, which sees its 25th anniversary next week.

Kong had an exchange last Friday with a user named "I am a sparkling red star" who claimed to have been part of the security forces deployed during the crackdown and argued that Beijing had no choice but to dispatch troops in order to control chaos.

"Nonsense," Kong replied, according to an archive of the deleted post saved by the anti-censorship website FreeWeibo. "There were no riots at all. You all opened fire on the masses and bloodily gunned them down, then tried to frame them after the fact. Can you name one student who started the rioting?"

Kong went on to decry the deaths of "hundreds of patriotic citizens", according to a report on Sunday in the Hong Kong-based Ming Pao newspaper. Attempts by AFP to access Kong's Weibo on Tuesday returned an error message that the account was "suspect".

China's ruling party tightly controls online expression, with a vast network of censors swiftly deleting postings on topics such as official corruption, criticism of top leaders or sensitive eras of Chinese history.

The lead-up to next month's Tiananmen anniversary, however, has seen an especially harsh clampdown, with prominent Chinese human rights lawyers, journalists and others detained for attending gatherings on the topic.

The bloody Tiananmen Square crackdown - which saw hundreds of peaceful demonstrators killed, by some estimates more than 1,000 - remains one of the most sensitive political issues in China. Some Chinese Internet users responded with puzzlement on Tuesday, noting that the professor is a staunch nationalist rather than a liberal or harsh government critic, the types of commentators whose accounts are typically deleted.

"Sina, you've gone too far," one user wrote. "Why did you ban Kong Qingdong?! This shows us how brain-damaged you've really become!"