An execution chamber is seen from the "button room" at the Tokyo Detention Center
Brad Pitt is the latest big star to join Weibo, China's largest micro blogging site

The film star Brad Pitt recently announced on the micro-blogging site that he was visiting China, a country he is said to be banned from because of his role in the 1997 film Seven Years In Tibet. The government was apparently upset about the film's portrayal of harsh Chinese rule there.

"I'm coming," he messaged via his mobile. "Yup, it's the truth."

His six-word text was forwarded more than 47,000 times and within an hour Pitt had gained more than 100,000 friends.

However, a few hours later the message was deleted, as censors withdrew it, to shore up "The Great Firewall of China".

In China, Twitter and Facebook are banned and there are strict rules that apply to information and messaging put out on Weibo, the largest Chinese micro-blogging platform.

More than 1,000 people are employed to keep an eye on the content of the micro-blogging site. Users of the site often have to wait for up to a week before their messages are approved.

On an average day, around 10 million messages are deleted.

The Chinese government is believed to be using Weibo to promote propaganda, with around 300,000 people posting pro-Communist party messages. Known as the 50 Cent Army, they get approximately 5p per post.

Any unauthorised messages that manage to make it through the censorship line, result in large fines and blocking of blogs.

Some users try to get around the system by using nicknames or code words for forbidden phrases.

The website has more than 350 million registered users and gains around 12 million new users every month.

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Chinese actress Yao Chen recently messaged on Weibo the words of Alexander Solzhenitsyn in a show of support against censorship

The most popular user is Chinese actress Yao Chen, with 33.2 million followers. Not far behind is the Chinese American pop star Wang Leehom, who currently has 28.6 million followers.

  • Sina Weibo has about 400 million users, but given the size of the world's Chinese-speaking population, it could overtake Twitter one day
  • The German carmaker Mercedes-Benz (China) Ltd sold a limited edition of its smart cars on Weibo
  • Lady Gaga is top of the Twitter charts with 33.1 million followers, second is Justin Bieber with 32.9 million and Katy Perry currently in third place with 31.2 million
  • American actor Ashton Kutcher became the first Twitter user to have more than a million followers

As Brad Pitt joins Weibo, one of Britain's most prolific Tweeters has left the site.