China continued its latest crackdown on dissent Thursday by sentencing a man to eight years in prison for advocating constitutional democracy and criticizing the ruling Communist Party.

The lawyer for 27-year-old Cao Haibo says his client was sentenced for “subversion of state power” at a secret court hearing in the southwestern city of Kunming. He says Cao, who worked at an Internet cafe, posted pro-democracy articles on a popular online messaging service.

Beijing authorities have carried out a campaign to silence critics in the lead-up to the once-a-decade power handover, which begins next Thursday with the 18th Party Congress.

Rights groups say prominent dissidents have been placed under house arrest or given other severe restrictions, while the capital of Beijing is in a state of virtual lockdown as the date of the meeting gets closer.

Police arrested Cao in October 2011, just three months after he married. His wife, Zhang Yan, told reporters that she was shocked at the severity of the sentence, adding that she did not know whether he would appeal.

Subversion of power is a vaguely defined charge that is often used to silence critics of the Communist Party. Those who face subversion, or the lesser charge of inciting subversion, are rarely acquitted by Party-controlled courts.

In February, a court sentenced democracy activist Zhu Yufu to seven years in prison for “inciting subversion” by posting a poem calling for mass protests like those that have recently swept North Africa and the Middle East.