Microblog users in Beijing who do not register using their real names by mid-March will be banned from posting comments, a local official said Wednesday, as authorities tighten their grip on the web.

The Chinese capital recently ordered users of weibos -- popular microblogs similar to Twitter -- to register using their real names, making it easier for authorities to track them if they post sensitive material.

The move comes as nervous authorities tighten their grip on the Internet amid fears it could help fuel unrest as China prepares to undergo a once-in-a-decade leadership transition this year.

An official at the Beijing government surnamed Tian told AFP that from March 16, those who failed to register with their real names would no longer be able to post or repost comments, but refused to provide more details.

According to the official Xinhua news agency, users who do not comply will not be kicked off microblogs altogether as they will still be able to read other people's postings.

Beijing was the first city to introduce real-name registration rules to curb the spread of "rumours and vulgarities", and since then, other cities such as Shanghai, and the south's Guangzhou and Shenzhen, have followed suit.

With more than half a billion Chinese now online, authorities are concerned about the power and influence of the Internet to spark unrest in a country that maintains tight controls on traditional media.

The government already censors the web in a system dubbed the "Great Firewall of China".

But despite the controls, people are still using weibos to vent their anger and frustration over official corruption, scandals and disasters by re-posting information and images as fast as the authorities can take them down.

Residents in the southern province of Guangdong protesting against land seizures and a power plant in December posted photos and reports on weibos, defying official efforts to block news of the incidents.

At least one of the protests ended with an apparent victory for local residents.