BEIJING China on Tuesday detained a prominent human rights lawyer on a charge of "causing a disturbance", two lawyers said, after he attended a weekend meeting that urged a probe of the bloody suppression of pro-democracy protests in Tiananmen Square in 1989.
Pu Zhiqiang, a leading free-speech lawyer, has represented many well-known dissidents, including artist Ai Weiwei and activists of the "New Citizens' Movement", a group that has urged Chinese leaders to disclose their assets.
He is also well known for opposing China's system of forced labour camps, which the government has abolished, and featured prominently in state media for that campaign - unusual for a government critic.
The move to formally detain Pu underscores the sensitivity of Chinese leaders to any form of criticism ahead of the 25th anniversary of China's crackdown on the demonstrations around Tiananmen Square in Beijing on June 4, 1989.
"Pu is very influential and has a following in the mainstream audience," said Maya Wang, a China researcher for New York-based advocacy group Human Rights Watch.
"The detention, as in previous years' house arrest, is meant to, first, put him out of action during this period, but more importantly, it might be a message to deter any others from commemorating the massacre during this important anniversary."
At least five dissidents and professors have disappeared since attending the meeting, held to commemorate the 1989 crackdown as well as "explore its implications and consequences and call for an investigation into the truth of June 4," said Hua Ze, a human rights activist.
In Pu's detention notice, Beijing police said they had "criminally detained" him on a charge of "causing a disturbance" and were holding him at the Beijing No.1 Detention Centre.
Pu's colleague Xia Lin, and a human rights lawyer, Zhang Sizhi, confirmed the detention, citing a member of Pu's family. Zhang said he could be representing Pu.
State security officers had searched Pu's office and home before his disappearance, said another rights lawyer, Zhang Qingfang.
Beijing police and detention centre officials declined to comment. Foreign Ministry spokeswoman Hua Chunying said she was "not familiar with the situation", when asked about Pu's detention at a daily news briefing.
The detention was discussed on Weibo, China's version of Twitter, drawing condemnation from hundreds of supporters, which government censors did not appear to be removing immediately.
"This is another heavy slap to anyone who harbours any illusions of the so-called 'new Xi-Li governance'," one microblogger wrote.
"As long as you express dissatisfaction with the government's actions, it can be packaged as 'causing a disturbance'," wrote another.
"This type of criminal charge fundamentally reflects the interests of the ruling class and doesn't reflect the will of the people."
The charge of causing a disturbance appears to be "a catch-all charge that has increasingly been used to suppress dissent and crackdown on activism during 'sensitive' events," said William Nee, a China researcher of rights group Amnesty International.
For China's ruling Communist Party, the 1989 demonstrations that clogged Tiananmen Square in Beijing and spread to other cities remains taboo, all the more so in this sensitive 25th anniversary year.
The anniversary of the date on which troops shot their way into central Beijing in 1989 has never been publicly marked in mainland China, though every year there are public commemorations in Hong Kong.
The Chinese government has never released a death toll for the crackdown, but estimates from human rights groups and witnesses range from several hundred to several thousand.
Chinese President Xi Jinping's administration has ratcheted up pressure on dissent, detaining and jailing activists, clamping down on Internet critics and tightening curbs on journalists in what some rights groups call the worst suppression of free expression in recent years.
Pu, who participated in the 1989 pro-democracy movement, had vowed to return to Tiananmen Square every anniversary.
"For me these visits have also aroused guilt feelings," he wrote in a 2006 essay for the New York Review of Books.
"The government's pressures to forget June Fourth have caused the day slowly to erode in public memory: each year the Tiananmen Mothers seem more isolated, and the massacre seems more a topic to be avoided in daily conversation.
"Our Tiananmen generation is now in middle age; we are in positions where we can make a difference. Do we not want to?"
(Additional reporting by Ben Blanchard, Maxim Duncan and Megha Rajagopalan; Editing by Clarence Fernandez)