BEIJING — A legal research center in Beijing was shut down Friday and the licenses of more than 50 lawyers — many known for their politically sensitive human rights work — were revoked in what appeared to be one of China's most drastic moves to restrain activist lawyers.

The actions underscore a renewed official push to control these lawyers, who already run the risk of being detained, harassed, attacked and threatened with disbarment for their work. China is also preparing for the communist state's 60th anniversary on Oct. 1 — a particularly sensitive period when dissent is not tolerated.

About 20 officials from Beijing's Civil Affairs Bureau showed up Friday morning at the offices of the Gongmeng rights group's legal research center and confiscated computers and other equipment, said office manager Tian Qizhuang. They also questioned researchers and other employees on the nature of their work.

"They said the research center was not properly registered," Tian said. "We didn't want to resist them, but what they are doing violates the law. ... Shutting us down is the same as shutting down Gongmeng."

Xu Zhiyong, a legal scholar who works with Gongmeng's lawyers, said the legal center was a department of the Gongmeng group, which has proper registration.

Xu said the center does legal research on public welfare and offers legal aid. Most recently, lawyers from Gongmeng represented parents whose children got sick in a widespread scandal involving milk tainted with the industrial chemical melamine.

"We are upholding social justice. We're helping the weakest people," Xu said. "The people who hurt them, the people who are high up, they really don't want us to exist. But we believe that conscience triumphs over the black and evil forces."

The legal center's shutdown came two days after Beijing's tax bureau fined the group 1.4 million yuan ($200,000) because it said the group had not paid taxes.

Xu, who has arranged for a hearing with the bureau, said there had been only a delay and that the full amount had been paid.

"The tax bureau levied the heaviest fine to us. It's not fair," he said.

Neither the tax bureau nor the civil affairs bureau responded to faxed questions regarding the shutdown.

In addition, the licenses of 53 lawyers in Beijing have been canceled, effectively banning them from working.

A notice posted last week on the Beijing Justice Bureau's Web site said the lawyers had been penalized because they did not pass an assessment by their firms or failed to register with the bureau.

The notice gave no details other than a list of names, including Jiang Tianyong, who recently defended a Tibetan Buddhist cleric against charges of concealing weapons in an area of China where anti-government protests occurred.

"We have lost the trust of the government and party. That's why we have this situation today," Jiang said. "But we feel like we have completely followed the law. I feel like China's laws have cheated us."

Amnesty International condemned the decision Friday as a major blow to the human rights movement in China.

"There are only a tiny group of lawyers left in China who are brave enough to take the risk of representing victims of human rights violations," said Roseann Rife, the group's Asia-Pacific deputy director. "A further crackdown against human rights lawyers is a major blow not only to these legal professionals but to the human rights defense movement in China."

Attorney Li Xiongbing, who has taken on cases involving the banned Falun Gong spiritual movement, said he was informed he no longer could practice law on June 30, when a court in northeast China barred him from entering. The court said it had been notified by Beijing's justice bureau that he had not passed his assessment.

Li is also a member of the Gongmeng group.

"This goes against the law in a powerful way," Li said. "I'm most concerned that the authorities are going against the principal of law and are cracking down on people in the legal profession. Which direction is our country going now?"