A court in Beijing denied an appeal by one of China’s best-known democracy advocates on Thursday and upheld his 11-year prison sentence, human rights activists said.

The Beijing Municipal Higher People’s Court upheld the conviction and unusually harsh sentence of the advocate, Liu Xiaobo. Mr. Liu, a Beijing scholar, played an important role in organizing a document called Charter 08 that called for political and legal reforms. Charter 08 was issued in December 2008; Mr. Liu was subsequently convicted of “inciting subversion of state power.”

The denial of Mr. Liu’s appeal marks the third judicial setback this week for activists in China and the latest signal that China’s leaders remain leery of tolerating greater pluralism.

Tan Zuoren, an activist who said the poor quality of the construction of public buildings contributed to the death toll in the Sichuan earthquake in May 2008, was sentenced to five years in prison on Tuesday for sending e-mail messages with comments about the military crackdown on protesters in Tiananmen Square on June 4, 1989.