Responding to reports of the detention by Beijing police of the university professor and at least six of his students and expressing Washington's concerns, U.S. State Department spokeswoman Jen Psaki in a statement said Tohti has been outspoken in his support of the human rights for China's ethnic Uighur citizens.
She said the detention "appears to be part of a disturbing pattern of arrests and detentions of public interest lawyers, Internet activists, journalists, religious leaders and others who peacefully challenge official Chinese policies and actions."
She said the United States calls on Chinese authorities to "immediately account for the whereabouts" of Tohti and his students and guarantee their protection and freedom "to which they are entitled under China's international human rights commitments, including the freedom of expression."
On Wednesday, Beijing police reportedly raided the home of Tohti before detaining him.
The economist is a professor at Beijing's Central University for Nationalities, the Voice of America reported, quoting his wife.
Tohti is a Uighur Muslim, a Turkic-speaking minority in China's far western ethnically-tense Xinjiang province. The region has been the scene of numerous clashes between the Uighurs and Chinese police, resulting in the deaths of dozens of people.
The VOA report quoted his wife as saying her husband had done nothing except writing articles on stability in Xinjiang.
The Chinese Foreign Ministry gave no details, only saying Tohti was detained "under suspicion of committing crimes and violating the law," VOA said.
The Xinjiang-Uighur region is close to the border with Pakistan and Afghanistan. The Uighurs resent being ruled by the majority Han Chinese. China maintains foreign Uighur groups linked to the banned East Turkistan Islamic Movement are to blame for the trouble in the region. However, the World Uighur Congress, based in Stockholm, Sweden, disputes the allegations.
Last month, the Xinjiang government said police shot and killed eight people after a terrorist attack on a police station. In the same month, 16 people, including two policemen, died in a similar clash.
Last October, Chinese authorities blamed Uighurs for a vehicle incident in Beijing's Tiananmen Square in which five people died including three in the vehicle, and 40 more were injured. In 2009, riots broke out in Urumqi, capital of the region, in which about 200 people died.
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