BEIJING (REUTERS) - China's foreign ministry expressed anger on Tuesday after a prominent detained Uighur academic won a human rights award in the United States, saying that he was a suspected criminal.

Ilham Tohti, an economics professor who has championed the rights of the Muslim Uighur people from China's restive far western region of Xinjiang, was detained in January and subsequently charged with separatism.

Prof Tohti's case is the latest sign of the government's hardening stance on dissent in Xinjiang, gripped by periodic outbursts of violence often pitting Uighurs against ethnic Han Chinese.

The PEN American Center said on Monday it would award Prof Tohti the 2014 PEN/Barbara Goldsmith Freedom to Write Award, and that his daughter, a student at Indiana University, will accept the award on her father's behalf in New York on May 5.

Chinese Foreign Ministry spokesman Hong Lei, asked about the prize, said Tohti was suspected of crimes.

"The relevant person is suspected of committing crimes.

China's public security organs are handling it in accordance with the law," Mr Hong told a daily news briefing. "No organisation or person should interfere with China's judicial sovereignty and independence."

Prof Tohti's case has attracted high-level concern in both the United States and European Union. His wife has called the allegations against him ridiculous.

"Tohti represents a new generation of endangered writers who use the web and social media to fight oppression and broadcast to concerned parties around the globe," PEN American Center President Peter Godwin said in an emailed statement.

"We hope this honour helps awaken Chinese authorities to the injustice being perpetrated and galvanises the worldwide campaign to demand Tohti's freedom." Unrest in Xinjiang has killed more than 100 people in the past year, prompting authorities to toughen their stance. Many Uighurs resent restrictions on their culture and religion, though Beijing says it grants them broad freedoms.

Last month, the government blamed Xinjiang militants for a knife attack in the southwestern city of Kunming, in which 33 died, including four of the attackers shot dead by police.

Advocates for Prof Tohti say he has challenged the government's version of several incidents involving Uighurs. That includes what China says was its first major suicide attack, in Beijing's Tiananmen Square in October, involving militants from Xinjiang, by pointing out inconsistencies in the official accounts.