Police in Hong Kong arrested an American lawyer under the city’s national security law on Wednesday, a source at his law firm told Reuters, hours after authorities arrested dozens of democracy activists under the controversial legislation.

John Clancey, chairman of the Asian Human Rights Commission and a member of a group linked to pro-democracy protesters in the city, was arrested as police raided the law firm Ho, Tse, Wai & Partners, said the source, who declined to be identified due to the sensitivity of the issue.

Hong Kong police did not respond to a request for comment.

Clancey is the treasurer of Power for Democracy, which was involved in an unofficial, independently organised vote in July 2020 to select opposition candidates for a since-postponed legislative election.

Earlier on Wednesday, police arrested dozens of pro-democracy activists linked to that vote, intensifying a crackdown on the movement since the security legislation was imposed on the city in June.

The source at the law firm based in the heart of the global financial centre confirmed Clancey is an American passport holder.

Footage posted online showed police officers arriving at the law firm which has represented several opposition figures in the Chinese-ruled city.