China began applying new rules governing online comments today, further threatening freedom of expression in a move authorities said was aimed at protecting national security.

The Asian giant is home to a dynamic and vibrant tech sector but internet censorship is pervasive, with many major foreign websites and apps blocked.

Social media platforms maintain armies of staff responsible for erasing messages deemed too politically sensitive.

However, many comments critical of power remain online along with a plethora of insults, rumours and defamatory messages.

The Cyberspace Administration of China previously drew up even stricter regulations on the moderation of online comments and they took effect Thursday.

"Service providers shall... carry out a credit evaluation of users based on their commenting behaviour," state the new rules, which were first published last month.

People who have been "seriously discredited" by their messages "will be placed on a blacklist" that will prohibit them from further commenting, even with a new account.

All users must register with their real name and identity card number.

The new regulations mainly apply to the comments sections of websites and apps.

The Cyberspace Administration said they would help "protect national security, the public interest and citizens".

State media praised the changes, saying "the internet is not a lawless zone". 

But internet users expressed only tepid support or objections.

"It limits antisocial behaviour, rumours and online violence, but you also have to hear people's aspirations and criticisms," said one user on the Twitter-like platform Weibo. 

Another user said the rules were not detailed and would "cut very wide".

"We hardly criticise them at all and already they can't stand it anymore," said a third person.

The regulations were proposed before rare demonstrations took place in cities across China last month to demand the lifting of anti-Covid restrictions.

News of the rallies managed to spread on social media despite strict censorship.