China has detained a prominent human rights lawyer on a charge of "causing a disturbance", two lawyers have said, after he attended a weekend meeting that urged an investigation into the bloody suppression of pro-democracy protests in Tiananmen Square in 1989.

Pu Zhiqiang, a leading free-speech lawyer who has represented many well-known dissidents, including artist Ai Weiwei, was detained by Beijing police in the early hours of Tuesday, according to Qu Zhenhong, an associate at Pu's firm in Beijing who has been in contact with his family.

Pu enjoys mainstream prominence that is unusual for most dissidents and news of his detention was circulating widely on Chinese microblogs.

The decision 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.

"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," said Maya Wang, a China researcher for New York-based advocacy group Human Rights Watch.

At least five dissidents and professors have disappeared since attending the meeting, held to commemorate the protests 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.

Discussion taboo

Pu had taken part in the 1989 demonstrations when he was a graduate student.

The tumultuous protests lasted seven weeks before being crushed by army troops backed by tanks, who attacked the unarmed protesters near Tiananmen Square.

Public discussion of the crackdown still remains taboo inside the country, making the seminar Pu attended in Beijing an unusually bold event despite being held in a private residence with an attendance of only about a dozen people.

Meanwhile, activists said other participants in the seminar had been summoned by police after the event.

The mobile phones of most of the other attendees were turned off on Tuesday or rang unanswered, the AP news agency reported.

Pu has not yet been formally indicted. Beijing police had no immediate comment.

Source: Agencies