Gheyret Niyaz, 51, gave an interview to a Hong Kong newspaper one month after riots broke out in Xinjiang, leaving at least 197 people dead and 1,600 injured.

The riots were the deadliest ethnic clashes in China in decades, as local Uighurs, a Muslim minority with their own Turkic language, turned on Han Chinese civilians and burned stores and homes.

When Mr Niyaz gave the interview, Xinjiang was in the middle of a news blackout, during which international phone lines were cut and the internet was disabled.

The charge of endangering state security is a vague catch-all that is often used by officials to lock up people they believe are political threats. The same charge was recently used to convict Liu Xiaobo, the author of a pro-democracy petition called Charter 08. Mr Liu was also given 15 years in prison.

However, the sentence against Mr Niyaz is all the more harsh because he was an advocate of greater cooperation between the Uighurs and Han Chinese. A graduate of Minzu University in Beijing, he is a fluent Chinese speaker who has not called for Xinjiang independence and he did not take part in the rioting.

“Niyaz’s draconian prison sentence raises serious concern about the authorities’ respect for freedom of expression, and capacity and commitment to protect fundamental rights and freedoms,” said Sharon Hom, the executive director of Human Rights Watch in China.

“We are utterly astonished at the outcome of this trial,” said Reporters without Borders, an NGO for journalistic freedom. “Gheyret Niyaz did indeed make some criticism of Chinese policy in his region, but he is neither a criminal nor a dissident. He is seen by Uighurs based abroad as supportive of China’s administration of Xinjiang and even shares some of the Chinese government’s views of the summer 2009 unrest.”