Hong Kong democracy activist and media tycoon Jimmy Lai has been charged under the city's national security law on suspicion of colluding with foreign forces and endangering national security.
Mr Lai, 73, an ardent critic of Beijing, is the highest profile person charged under the sweeping new law imposed on the Chinese-ruled city in June.
The law has been condemned by the West and human rights groups as a tool to crush dissent. Authorities in Hong Kong and Beijing say it is vital to plug holes in national security defences exposed by months of sometimes violent anti-government and anti-China protests that rocked the city over the last year.
"After further investigation by the police's National Security Department, a 73-year old man is charged with one count of 'collusion with a foreign country or with external elements to endanger national security'," police said in a statement on Friday.
Mr Lai was denied bail earlier this month following his arrest on a separate charge of fraud related to the lease of a building that houses his Apple Daily, an anti-government tabloid.
The founder of the Next Digital media group had been a frequent visitor to Washington, where he has met officials, including Secretary of State Mike Pompeo, to rally support for Hong Kong democracy, prompting Beijing to label him a "traitor".
His arrest in August and a dramatic police raid on Apple Daily’s newsroom sparked an outcry from foreign governments including the UK, which said the law was being used to crack down on press freedoms in the former British colony.
British Prime Minister Boris Johnson’s spokesman, James Slack, said at the time that Mr Lai’s arrest was “further evidence that the national security law is being used as a pretext to silence opposition”.
A group of western envoys wrote an open letter in November condemning the erosion of media freedoms in the Asian financial hub, a situation they said had been worsened by Beijing’s imposition of the “vaguely defined” national security law.
News of the charges comes as authorities intensify a crackdown on opposition forces that has seen lawmakers dismissed and high-profile democracy activists such as Joshua Wong jailed.