Police in Hong Kong have arrested 53 pro-democracy activists on suspicion of subversion, which violates the national security law for the territory.
The police announced the arrests at a news conference on Wednesday.
The 53 were arrested on subversion charges linked to an unofficial vote organized by pro-democracy activists to choose candidates for a Legislative Council election that was to be held last September but was postponed.
Police say six of the people planned criminal activities and the other 47 took part in them.
Pro-democracy groups say the arrested include Wu Chi Wai, a former Legislative Council member and former head of the Democratic Party.
Jimmy Sham, a district council member who previously headed a group that called for massive protests, was also arrested.
The unofficial vote was designed to win a majority on the Legislative Council to reject the government's budget bill and force Chief Executive Carrie Lam to resign.
Police see this as an attempt to overthrow the government, in violation of the national security law for Hong Kong.
Wednesday's mass arrests are the largest since the law went into effect on June 30 last year. It's also believed to be the first time anyone has been charged with subversion in Hong Kong.