Chinese Avant-Garde artist Ai Weiwei is pictured at the Theater am Goetheplatz in Bremen, northern Germany, on Sunday, Oct. 4, 2009. (FOCKE STRANGMANN/AP)

The Chinese government on Thursday confirmed it is holding the missing artist Ai Weiwei, who has been incommunicado since police seized him Sunday at Beijing’s airport while other officers raided his art studio.

A foreign ministry spokesman said Ai, an outspoken critic of the government, was being investigated for “economic crimes” and warned other countries not to meddle in the case.

“China is a country ruled by law and will act according to law,” said Hong Lei, the foreign ministry spokesman, at a regularly scheduled press briefing. “We hope that the countries concerned will respect China’s decision.”

“This has nothing to do with human rights or freedom of expression,” Hong said, adding: “Other countries have no right to interfere.”

Reporters pressed the spokesman several times for more details on Ai’s detention, but he refused to say more. Hours later, in an odd development, the foreign ministry issued an official transcript of the Thursday briefing that deleted all the questions and answers about Ai. Typically, the briefing transcripts appear on the ministry Web site unaltered.

Xinhua, the state-run news agency, issued a brief, one-line report late Wednesday saying Ai was suspected of economic crimes. But that posting, too, was soon redacted from the Xinhua Web site. Some Internet users took a screen shot of the original Xinhua post before it was erased and displayed it on their Twitter accounts.

During the foreign ministry briefing, Hong did not elaborate on the charges against Ai. Chinese authorities sometimes use “economic crimes,” and specifically tax evasion charges, to try to silence dissenters.

Ai, a conceptual artist whose work has been displayed around the world, is the most prominent figure arrested so far in a sweeping security crackdown in China that has netted dozens of human rights lawyers, activists, writers and bloggers. The U.S. State Department, the European Union and various human rights groups have called for the release of Ai and all the detainees.

The Chinese media have been largely silent about Ai’s disappearance. But the nationalist tabloid, Global Times, which is owned by the Communist Party newspaper People’s Daily, ran a second, blistering editorial Thursday under the headline “Western critics will not change China.”

The editorial said China needed to control “people like” Ai to maintain social stability, and said “the goal of Western criticism of China’s human rights is to disrupt China politically.”

Since populist street uprisings this year began rattling authoritarian regimes in the Middle East and North Africa, China’s communist rulers have become nervous about the unrest spreading here.

The authorities have responded with dual approach — a heavy-handed security clampdown on the one hand, including the detentions of activists and new restrictions on foreign journalists; and promises, on the other hand, to address the grievances of ordinary Chinese, like soaring housing prices and high-level corruption among the ruling elite.

The clampdown has targeted some longtime activists and human rights lawyers, as well as some writers and Internet bloggers who are believed to have been instigating Middle East-style “jasmine” protest rallies against the ruling Communist Party.

Among those arrested was Ran Yunfei, a prominent writer and editor of a literary magazine in Sichuan province, who on March 25 was formally charged with “inciting subversion of state power” for essays he posted online about the jasmine revolutions in the Middle East.

“When the Egyptians cheered the departure of [Hosni] Mubarak at Liberation Square on February 12, they maybe didn’t think there are some sleepless netizens in Far East, cheering for the rebirth of Egypt on Twitter, Facebook and other websites,” Ran wrote in one lengthy, 5,000-word essay in mid-February. “Some netizen made a joke, saying China is like an old bachelor, looking on with envy while a guy and a girl next door enter into their honeymoon suite.”

Human rights campaigners and others said they found the current round of arrests, especially involving the bloggers like Ran and also Ai, particularly sinister. They said the authorities seem to be targeting opinion-makers who expressed personal views on the Internet and on microblogging sites like Twitter, which have lately generally enjoyed slightly more latitude for exchanging views even on controversial topics.

Zhao Lianhai, an activist who was jailed for assisting parents of children sickened by contaminated baby powder, has added his voice to those calling for the release of Ai and the other recent detainees.

Last November, Zhao was ordered jailed for two and a half years for incitement. But he was released for medical reasons a month later, and his whereabouts remain unknown.

“Firstly, we should criticize the serious mistake currently being made by the authorities, and also, we kindly hope that the authorities will correct their serious mistake in time, release all the newly arrested dissidents, and solve all the problems via negotiation in the frame of the laws,” Zhao posted on his Twitter account late Wednesday. “This is the best way to solve problems and the only choice to avoid disaster.”

Staff researcher Zhang Jie contributed to this report.