Prominent Uighur scholar Ilham Tohti was charged by Chinese authorities with “separatism” on Wednesday. The long-expected announcement came amid a period of violent unrest in China’s far-western Xinjiang Uighur Autonomous Region.

The Beijing-based professor of economics is a moderate but determined critic of China’s treatment of ethnic minority groups. He has been held since January, but was not allowed to see his lawyer until June. His lawyer, Li Fangping, only heard about the charges when the local government posted the news online, the Guardian reports.

Charges against Tohti come at a particularly sensitive time. This week alone, dozens were killed or injured in violence outside the ancient city of Kashgar. Beijing blamed the unrest on Uighur extremists, but human-rights groups claim Chinese authorities exaggerate terrorist ties in order to justify their own use of force. On Wednesday, an imam in the city of Kashgar, who was frequently quoted by state media as praising the Communist Party and denouncing terrorism, was reportedly stabbed to death.

Chinese authorities allege that Tohti used a website to, among other things, “spread separatist thinking,” and accuse him of urging his students to engage in violent struggle — charges at odds with his extensive body of writing and work. Rights groups say the charges amount to a political witch hunt, and show Beijing’s unwillingness to tolerate even the most moderate and measured criticism.

PEN American Center, which awarded Tohti the PEN/Barbara Goldsmith Freedom to Write Award earlier this year, condemned the indictment in a statement, saying that he “has worked within the country’s laws to promote equal rights for all of China’s citizens, and to encourage exchange and understanding between different ethnic groups.”

The charge against Tohti will almost certainly lead to conviction and, potentially, the death penalty.