BEIJING (REUTERS).- The dissident Chinese artist Ai Weiwei, whose detention in April ignited an international uproar, was released on bail Wednesday under conditions likely to keep the outspoken critic of Communist Party controls silent for now.

"I can't say anything more, because I'm on bail," Ai told reporters who had gathered outside his home after his release was reported by China's official Xinhua news agency.

His abrupt release came days before Chinese Premier Wen Jiabao heads to Europe, where Berlin and other capitals have been critical of Beijing's secretive detention of Ai and dozens of other rights advocates, lawyers and dissidents.

But the Chinese government cast its apparent backdown as a vindication of their controversial case. Xinhua said Ai was freed "because of his good attitude in confessing his crimes as well as a chronic disease he suffers from," citing the police.

A company that police said he controlled "was found to have evaded a huge amount of taxes and intentionally destroyed accounting documents, police said," according to Xinhua.

"The decision comes also in consideration of the fact that Ai has repeatedly said he is willing to pay the taxes he evaded," said the report.

Family members and supporters have said the outspoken 54-year-old artist was a victim of a crackdown on political dissent that intensified after overseas Chinese websites in February called for protests in China to emulate anti-authoritarian uprisings in the Arab world.

China's courts and police are firmly controlled by the ruling Communist Party, and it is unusual, but not unprecedented, for authorities to back away from a potential prosecution in a high-profile case like this.

"Without the wave of international support for Ai, and the popular expressions of dismay and disgust about the circumstances of his disappearance, it's highly unlikely the Chinese government would have released him," said Phelim Kine, a researcher with Human Rights Watch, a New York-based advocacy group.

The United States, Germany, Britain and other governments voiced concern about Ai's secretive detention without formal notification to his family. Chinese Premier Wen will visit Britain and Germany, as well as Hungary.

"I'm perfectly fine. My health is fine," Ai, notably thinner after his months in detention, said in brief comments to Britain's ITV news service. He thanked his supporters.

German Chancellor Angela Merkel's chief spokesman Steffen Seibert said she welcomed Ai's release. "Today's release on bail can only be a first step. Now the case against Ai WeiWei has to be cleared in a constitutional and transparent way," he added.

State Department spokesman Mark Toner also said Ai's release was welcome, adding: "But there's obviously more individuals who are being held, so we want to see the release of all these people."

RETURNED HOME, HEALTH OKAY

Ai (whose name is pronounced "Eye Way-way") was detained at Beijing airport on April 3, igniting an outcry about China's tightening grip on dissent, which has triggered the detention and arrest of dozens of rights activists and dissidents.

The bearded, burly contemporary artist was the most internationally well-known of those detained, and his family has repeatedly said that he was targeted by authorities for his outspoken criticism of censorship and Communist Party controls.

Amnesty International said Ai's release was an "important" but limited step, and urged Beijing to release other activists and dissidents held in the recent crackdown that has relied heavily on extra-judicial detentions.

"His release can be seen as a tokenistic move by the government to deflect mounting criticisms," said Catherine Baber, the Asia-Pacific deputy director for Amnesty, in emailed comments.

"It is vital that the international outcry over Ai Weiwei be extended to those activists still languishing in secret detention or charged with inciting subversion," she said.

In China, bail can be used to release suspects on condition that they do not break laws for a stipulated time, and that condition may discourage Ai from speaking out or resuming his campaigning against government targets.

"There are well-grounded concerns that the conditions for Ai Weiwei's release will be onerously restrictive," said Kine, the Human Rights Watch researcher.

The well-known British sculptor Anish Kapoor said foreign artists should still not show their work in China for now.

"While I am thankful that he has been released, I do not think that artists should present their work in China until the situation has been resolved," he said in an emailed statement about Ai's release.

(Additional reporting by Paul Eckert in Washington; Writing by Sanjeev Miglani; Editing by Ron Popeski and Alistair Lyon)