The prosecutors' office of the municipality of Tianjin posted on its microblog that Zhou Shifeng, a lawyer who heads a Beijing-based firm seen as being at the centre of the security sweep, has been charged with subversion of state power. Three activists were indicted on the same charge, the prosecutors' office said.
The vaguely defined charge carries a maximum sentence of life imprisonment.
China launched its largest-ever crackdown against human rights lawyers and activists on July 9, 2015, seizing and questioning hundreds of people nationwide in a campaign that sent a chill through the country's legal system. Nearly two dozen of them remain in detention and face charges, including subversion and inciting subversion of state power.
On the one-year anniversary of the crackdown last week, overseas bar associations and lawyers' groups issued an open letter to Chinese President Xi Jinping criticising the detentions. The letter adds to international expressions of concern, including from some Western governments, over the crackdown.