HONG KONG (Reuters) - More than 200 protesters gathered on Thursday at a Hong Kong university to condemn the expulsion of a student defending free speech, in what was seen as another incremental sign of eroding freedoms in the Chinese-ruled city.

Hong Kong, a former British colony, reverted to Chinese rule in 1997 with the guarantee of a high degree of autonomy and civil liberties including academic freedoms and free speech not permitted in mainland China.

But since the 2014 pro-democracy “Umbrella Revolution” street occupations that blocked major roads, there has been a gradual tightening of civil liberties and individual rights, especially against a younger generation of student activists who spearheaded the protests.

The latest row involved a controversy over a so-called “democracy wall” at the Polytechnic University - a public notice board, common in many Hong Kong universities, designated as a free space for expression, political or otherwise.

Last September, the university decided to cover up part of the wall after slogans advocating independence for Hong Kong were posted, prompting a group of students to storm up to the university administration offices, demanding the democracy wall be free from censorship. A skirmish broke out between the students and several guards.

After months of deliberation, four students were punished last Friday, including a post-graduate nursing student, Gerald Ho, who has openly advocated independence for Hong Kong, a red line for Communist Party rulers in Beijing.

A former student union leader, Lam Wing-hang, was suspended from his studies for a year, while two others were ordered to do community service.

The protesters demanded the punishments be rescinded, echoing a joint statement put out by a coalition of student union bodies in more than 10 tertiary institutions demanding free speech be respected on campus.

“The absence of clear sentencing guidelines renders the verdicts highly unjust and unacceptable. The intention of the university authorities to create a chilling effect for eradicating all ‘sensitive views’ is crystal clear in this case,” the statement read.

Lam said he didn’t regret trying to safeguard students’ rights.

“I am not afraid of white terror,” he told the crowd, referring to the university’s heavy-handedness and lack of a legal basis for the punishments.

China considers Hong Kong its inalienable territory and considers any advocacy of independence to be taboo and a violation of Hong Kong’s mini-constitution, or Basic Law.

In 2017, the heads of 10 universities in Hong Kong released a joint statement saying that they did not support Hong Kong independence as it contravened the Basic Law.

The university gave no immediate response to a Reuters request for comment. But the institution’s interim president, Philip Chan, said in an earlier mass email to students that violent acts on campus wouldn’t be tolerated.