Postcard from... Beijing

Testing the sense of humour of the Chinese Communist Party can be a very risky business indeed, as one Chinese blogger has discovered to his cost.

Tweeting during the 18th Communist Party Congress this month amid an extremely tight security crackdown, Zhai Xiaobing (pictured) quipped how the next film in the "Final Destination" horror franchise would be about the Great Hall of the People collapsing on party delegates. "An earthshaking debut will be seen at the global premiere on November 8!" he tweeted. "Later, one-by-one the survivors die in strange ways. Is it the game of god, or the devil venting his wrath? What does the mysterious number 18 have to do with opening the gate to hell?"

In the run-up to the event, security officials sent activists out of Beijing and rounded up hundreds of petitioners who came to the capital to lobby the central government about their local grievances.

Mr Zhai's Twitter account went quiet after the post, and friends who went looking for him in the Beijing suburb of Miyun found he was gone. Police said he was being investigated for "spreading terrorist information." There were reports his wife was also missing.

It is surprising the offending witticism ran on Twitter, which is banned in China, showing how deep the penetration of China's net nannies can be. Around 35 million people use Twitter in China, despite the ban, accessing the service using a Virtual Private Network (VPN).

Hundreds of people have signed an online petition calling for Mr Zhai's release and calling the allegations against him absurd.