Chinese authorities have detained Pu Zhiqiang, one of the country’s most visible and prominent rights lawyers, after he attended a meeting held to discuss the June 4th Tiananmen Square crackdown.

The small gathering, held in Beijing on  May 3, involved prominent liberal intellectuals, dissidents and several whose lives were altered drastically in the wake of the 1989 crackdown. Most of the nearly 20 attendees were taken away by authorities for questioning in the days after the meeting, with some allowed to return home. In addition to Mr. Pu, rights groups and lawyers say four others who attended the meeting were also formally detained, though CRT could not immediately verify those reports.

Authorities have been particularly nervous as this year’s Tiananmen Square anniversary approaches, as this year marks a quarter century since the crackdown.