Chinese authorities have been especially sensitive to any perceived dissent about the party meeting, which closed last week after ushering in a new generation of leaders. Ahead of the event, police sent activists out of Beijing and rounded up the hundreds of people who tried to draw the attention of central authorities to their grievances against local governments.

Zhai Xiaobing's Nov. 5 tweet suggested the next movie in the "Final Destination" horror franchise would be about the Great Hall of the People collapsing on party delegates.

After Zhai's Twitter account fell silent for a few days, Liu Yanping, a friend of his, grew worried and visited his home in Miyun county in Beijing's northeastern suburbs. There, his family members told Liu that Miyun county police had taken Zhai away on Nov. 7 and seized his computer, Liu said.

A Miyun county police officer who would only give his surname, Sun, told The Associated Press on Wednesday that Zhai was being investigated for "spreading terrorist information." The charge carries a maximum penalty of five years' imprisonment.

"I was very shocked when I realized what happened to him. I've consulted a few lawyers and I feel that it's clear his Twitter joke does not amount to spreading terrorist information," Liu said. "It's just preposterous."

Zhai's wife, when reached by phone, declined to comment on her husband's situation.

The online petition, written by outspoken blogger and free speech advocate Wen Yunchao, urges authorities to lighten up.

"We solemnly request that Beijing police find a little sense of humor and not make a big deal out of nothing," the letter said. "In particular, do not destroy the goodwill and anticipation the public has for the new office holders after the 18th party congress by limiting and persecuting an ordinary citizen's normal freedom of speech in such a groundless fashion."

Further enquiries were directed to the Beijing Public Security Bureau, which did not immediately respond to a faxed list of questions.

A rights group said Zhai's case could be seen as a test of whether China's incoming leaders will continue a steady crackdown authorities have imposed on the country's small community of activists, dissidents and lawyers in recent years.

"The new leadership has two choices: continue down the path of criminal prosecution to signal that they are unwilling to change, or release Zhai to show goodwill that it is responding to popular demands for greater freedom," said Maya Wang, a Hong Kong-based Asia researcher for Human Rights Watch.