Berlin -- China has blocked a website inviting users of microblogging site Twitter to comment on the fall of the Berlin Wall amid a deluge of protests at Beijing's Internet censorship, organisers said Thursday.

The site was meant to be a place for people to share memories of the night the Berlin Wall was yanked down 20 years ago, but quickly morphed into a forum for protest against what users described as "The Great Firewall of China."

Of the roughly 3,300 comments left on the virtual wall, around 1,500 have been in Chinese, said Carsten Hein, coordinator of the "berlintwitterwall.com" project.

The site "has not been freely accessible since Monday evening Beijing time," he added, citing "several current sources."

According to the China Digital Times, one user wrote: "Mr Hu Jintao, please tear down this Great Firewall," in a twist on the famous 1987 Berlin speech by then US President Ronald Reagan who implored his Soviet counterpart Mikhail Gorbachev to "Tear down this wall."

Another said: "My apologies to German people a million times (for taking over this site). But I think if Germans learn about our situation, they would feel sorry for us a million times."

One apparently bemused German user wrote on the site: "The Berlin Wall speaks Chinese!"

The hugely popular Twitter site allows users to post a short message of no more than 140 characters which can then be read by other followers of the service.

China regularly cracks down on online content it deems unhealthy, which includes pornography and violence but also information critical of the government.

In June, the government was forced to backtrack on an order to install Internet filtering software on all computers sold in China after it triggered a huge outcry at home and abroad.

China has at least 338 million Internet users, more than any other country in the world, according to state media.

AFP/Expatica