A teenage former activist leader in Hong Kong has become the first public political figure to be prosecuted under a national security law imposed by Beijing. Tony Chung was trying to seek asylum at the US Consulate.

The former leader of the Hong Kong pro-independence group Student Localism, Tony Chung, was charged with secession, money laundering and conspiracy to publish seditious content on Thursday.

The charges against the 19-year-old come two days after plainclothes police arrested him in a coffee shop across the street from the US Consulate.

A supporting group, Friends of Hong Kong, said it was trying to arrange for Chung to enter the consulate and apply for asylum shortly before his arrest. Chung, who has been in police custody, has not been able to comment on whether he was attempting to seek asylum.

Chung was denied bail following his arrest on Tuesday. If he is found guilty, Chung could spend the rest of his life in prison. Two other activists who were arrested on Tuesday were released on bail.

Student Localism was a group that advocated for Hong Kong's independence from Chinese rule. The group disbanded just before Beijing imposed a controversial national security law on June 30. International chapters of Student Localism still exist.

Chung was previously arrested in July on suspicion of being involved in an organization promoting an independent Hong Kong.

Beijing said the security law was necessary to bring stability to the former British-ruled city after anti-mainland protests rocked Hong Kong. Critics of the law have said China officials use it to crush freedoms granted to the city after it returned to Chinese rule in 1997.