A Chinese court has charged veteran democracy activist Zhu Yufu with subversion for publishing a poem online urging people to gather and call for greater freedoms, his lawyer said on Wednesday.

The charges against Zhu, who previously served nine years in jail and has been in detention since March, centre on a poem posted on the Internet in which he calls on the Chinese people to "take to the square to make a choice".

He was detained as part of a widespread crackdown on dissent that took place early last year in China after anonymous online calls for protests similar to those that swept the Arab world.

"Zhu Yufu was charged with inciting subversion of state power for writing his poem and putting it online," the 60-year-old's lawyer Li Dunyong told AFP. "Zhu believes we all have the right to express ourselves freely."

Li said he had seen his client in good health in detention on Monday in the east China city of Hangzhou, and that the trial would take place some time after next week's Spring Festival.

Zhu was jailed between 1999 and 2006 for founding the "Opposition Party" magazine, serving another two years in prison from 2007 after he confronted a policeman who had questioned his son.

"We are not optimistic that Zhu Yufu will get off easily," Sarah Schafer, a China researcher for Amnesty International told AFP. "We hope that the court realises this man has not committed a crime and therefore should be released."

Subversion charges are vague, Schafer said, and often used to jail government critics. Nobel Peace Prize winner Liu Xiaobo was convicted on the same charge in 2009 and sentenced to 11 years in prison.

Late last year, Chinese courts handed unusually long jail sentences of nine and 10 years to longtime dissidents, Chen Wei and Chen Xi, who faced separate subversion charges.

"Like them, Zhu has not abandoned his activism through the years despite government retaliation. From the government's point of view, he's a recidivist and will be punished harshly," Wang Songlian of the Hong Kong-based group China Human Rights Defenders told AFP.

Zhu's poem, "It's Time", features the lines, "It's time, Chinese people! The square belongs to everyone. The feet are yours it's time to use your feet and take to the square to make a choice."

The Hangzhou People's Intermediate Court refused to comment on his case.