The U.N.'s top human rights official has condemned the harsh prison sentences that China has recently handed down against pro-democracy activists.

A statement issued Monday in Geneva by Navi Pillay, the United Nations High Commissioner for Human Rights, specifically mentioned prominent dissident Chen Xi, who earlier in the day received a 10-year sentence, and Chen Wei, who on Friday was sentenced to nine years, both for inciting subversion.

Pillay called the sentences a serious setback for the protection and promotion of human rights in China and evidence of an escalating clampdown on the activities of human rights defenders.

The statement also took note of the sentencing 10 days ago of prominent human rights lawyer Gao Zhisheng, who was ordered to serve three years in prison just as his five-year probation was due to expire.

The short trial against Chen Xi took place Guiyan, the provincial capital of Guizhou province. Chen Xi, a leader of the 1989 Tiananmen democracy protests, maintained his innocence but said he would not appeal.

Inciting subversion is a charge often used to punish dissidents critical of the ruling Communist Party.