Weibo, China's most popular microblogging platform, is operated by Sina Corp.

It is billed as the world's fastest-growing microblogging site but new users of Weibo are being warned that the rigid censorship that governs it means that tweets could take up to a week to get through.

In China, Twitter, Facebook and YouTube are banned over government fears that unconstrained internet access could undermine party rule.

Weibo, which is similar to Twitter, was launched in 2009 and allows users to post 140 character "tweets" and gather followers.

But while Twitter users have free reign over their accounts, strict rules apply to information and messaging on Weibo and an army of 1,000 censors monitor uploaded content.

Weibo users often have to wait up to seven days for a ­message to be approved and it is believed that around 10 million messages are deleted on an average day.

One example of censorship cited by critics is the response to searches for information about top officials such as former president Hu Jintao, which read: "According to related laws and regulations, search results are not shown."

Internet expert Duncan Clark said the Chinese government used Weibo as a propaganda tool.

"They have devised things such as limiting the number of re-tweets and posts for a particular post or person," he told the Mirror.

"Social media are increasingly where stories break, and where public opinion is formed," said David Bandurski, a researcher at the University of Hong Kong's China Media Project.

"This is the major reason why government Weibo accounts are growing rapidly because they are one key way the government can stay on top of breaking stories and try to head off unwanted news, rumours or speculation."

Earlier this month, Hollywood actor Brad Pitt, one of the Weibo's newest fans, experienced the pitfalls of the website's strict censorship rules after he used it to announce plans to visit China.

Pitt was allegedly banned from the country in 1997 after playing the role of the young Dalai Lama's Austrian tutor in Seven Years in Tibet, a film criticised for its negative portrayal of Chinese officials.

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

His six-word post was forwarded more than 47,000 times and Pitt gained more than 140,000 followers.

However, within just a few hours, the Mr and Mrs Smith star fell victim to the Great Firewall of China and his tweet was deleted.

Weibo currently has more than 400 million users.