SHANGHAI — The departing American ambassador, Jon M. Huntsman Jr., criticized China’s human rights record on Wednesday in some of the sharpest public comments here yet by a United States official since the Chinese government began a crackdown on dissent this year.
Using a high-profile annual lecture on Chinese-American relations to make his final public address as ambassador, Mr. Huntsman said bluntly that prominent Chinese activists had been unfairly detained or jailed, naming Liu Xiaobo, the 2010 Nobel Peace Prize winner, who is serving an 11-year prison sentence for “subversion,” and Ai Weiwei, the Beijing artist who was taken into custody on Sunday.
Mr. Huntsman also accused China of wrongly imprisoning Xue Feng, an American geologist who was gathering information on the oil industry and accused of stealing state secrets.
“The United States will never stop supporting human rights because we believe in the fundamental struggle for human dignity and justice wherever it may occur,” said Mr. Huntsman, who leaves his diplomatic post this month amid speculation he may seek the Republican nomination for president.
Foreign diplomats normally avoid such open criticism of Chinese policies and actions here, to avoid complicating relations and embarrassing top officials. Usually, that restraint is especially in play in forums drawing an elite domestic audience or major media attention.
But Mr. Huntsman’s speech, made one day after the State Department called for Mr. Ai’s immediate release, praised the artist and other prominent activists, saying they “challenged the Chinese government to serve the public in all cases at all times.”
In Berlin, Germany’s foreign minister, Guido Westerwelle, summoned the Chinese ambassador to protest Mr. Ai’s detention. American and European Union officials have expressed concern about his safety.
Mr. Ai was detained Sunday while trying to board a flight to Hong Kong from Beijing. His studio and offices were raided, and his wife and a number of staff members were taken to police stations for questioning. All but one was released.
Xinhua, the state news agency, released a one-line report late Wednesday that said Mr. Ai’s economic activities were under scrutiny. “Police said late Wednesday they are investigating Ai Weiwei for suspected economic crimes in accordance with the law,” the report said. Mr. Ai’s wife, Lu Qing, told The Associated Press that the police seized computers and money from their home after he was detained at the airport.
Mr. Ai’s arrest appears to be part of the government’s attempt to stifle dissent among activists who may be trying to emulate the protests and demonstrations in recent months in North Africa and the Middle East. Chinese security officers have detained activists, tightened controls over the Internet and the Chinese news media, and harassed and threatened foreign journalists.
In his speech, Mr. Huntsman seemed to hint at the recent clampdown by saying, “Cutting off dialogue and suppressing the news media do not help.” He later added, “We cannot move forward if, when differences emerge, only one of us is fully engaged.”
Mr. Huntsman, a former governor of Utah and a fluent Mandarin speaker and experienced Asia hand, was appointed by President Obama in 2009. If he does seek the Republican nomination, the connection to the administration could count against him; a strong stance on China could serve as a counterbalance.
Ian Johnson contributed reporting from Berlin, and Edward Wong from Beijing.