BEIJING — The German soccer star Mesut Özil is the latest international sports celebrity to be at the center of controversy over China’s hard-line policies, igniting fury among Chinese internet users by denouncing the country’s mass detention of Muslims.
Mr. Özil, who is of Turkish heritage and plays for Arsenal, an English Premier League club, took on one of China’s most sensitive policies with his comments on Friday about Uighurs, a largely Muslim Turkic minority in Xinjiang, in northwestern China.
The Chinese authorities have held as many as a million Uighurs, and possibly more, in indoctrination camps meant to drastically weaken their commitment to Islam. The internments have drawn international anger and led to legislation in the United States Congress that could impose sanctions on Chinese officials over the detentions, which China says are intended to deter terrorism.
“They shut down their mosques. They ban their schools. They kill their holy men. The men are forced into camps and their families are forced to live with Chinese men,” read identical posts on Mr. Özil’s Twitter and Instagram accounts, according to a translation by The Guardian.
“But Muslims are silent,” they read. “Don’t they know that giving consent for persecution is persecution itself?”
While some foreign celebrities and companies who have offended Chinese sensitivities in recent years seem to have done so unwittingly, there seems little doubt that Mr. Özil’s remarks were carefully chosen. His reference to Xinjiang as East Turkestan, a name for the region used by advocates of self-rule for Uighurs, made matters worse for many Chinese.
Arsenal quickly tried to distance itself from Mr. Özil’s posts, but the club’s response did not stave off a wave of online anger in China.
“The content posted was entirely Özil’s personal view,” Arsenal said in a statement early Saturday on Weibo, a social media platform that, like Twitter, allows users to share comments. “As a football club, Arsenal always adheres to the principle of keeping out of politics.”
That statement was not enough, many commentators in China said.
Some likened the controversy to one in October, when the N.B.A. was the target of condemnation. Daryl Morey, the general manager of the Houston Rockets, had issued a tweet (quickly deleted) that seemed to express sympathy with protesters in Hong Kong demanding democracy.
The N.B.A., in a statement in Chinese, said it was “extremely disappointed” by Mr. Morey’s tweet. But the N.B.A.’s commissioner, Adam Silver, then said that the league was committed to freedom of speech for its employees, drawing another round of anger from Chinese basketball fans and state media.
“Özil, you’re even worse than Morey!” read an online article in Global Times, a stridently nationalist Chinese tabloid, on Saturday. It cited an outpouring of furious comment on the Chinese internet, including an announcement that a fan chat room devoted to Mr. Özil would close.
“As Chinese people we cannot accept this,” the chat room announced. “Where nationalist interests are concerned, nobody’s personal pastimes are worthy of mentioning.”
China’s internet is heavily censored, usually making it an echo chamber of officially approved opinion. Even so, many Chinese people do support the government’s harsh policies in Xinjiang, including the detention camps, which the government calls job training centers.
In his comments, Mr. Özil referred to the widespread reluctance of many Muslim-majority countries to openly criticize China over its policies in Xinjiang. Chinese officials may worry that his statement could inspire more Muslims abroad to demand action against Beijing.
Mr. Özil’s comments “hurt the feelings of the Chinese people,” the Chinese Football Association said in a statement quoted by The Paper, a news site based in Shanghai. “This is unacceptable to us,” the association said.
International debate about Xinjiang escalated in recent weeks after investigative reports from The New York Times and the International Consortium of Investigative Journalists that provided new details about the indoctrination camps.
The Chinese government has denounced the reports as false or as part of a conspiracy to foment ethnic unrest in Xinjiang. The government also issued English-language videos to make the case that China was menaced by extremist violence among Uighurs.
Many foreign experts argue that while anti-Chinese violence has been a problem in Xinjiang, the government has unfairly painted vast numbers of Uighurs as potential extremists and exacerbated ethnic divisions with its mass detentions.
If recent experience offers any guidance, Mr. Özil and Arsenal can expect days, maybe weeks, of bitter criticism from Chinese media and officials.
“It’s safe to say that this incident will damage the image of Özil and the Arsenal club in the eyes of Chinese football fans,” Hu Xijin, the editor of Global Times, wrote in a commentary. But he advised fans not to go too far and stoke international attention.
“I argue that we Chinese people should maintain a scornful attitude toward these kinds of people and their games,” he said.