Jailed former activist Joshua Wong has appeared in court charged with conspiring to collude with foreign forces under the National Security Law.

Wong, 28, is serving a sentence of four years and eight months for conspiracy to commit subversion for his involvement in an unsanctioned Legislative Council primary poll, in a plot to overthrow the government.

He was arrested in Stanley on Friday and taken to West Kowloon Magistrates' Courts in the afternoon to face one count of "conspiracy to collusion with a foreign country or with external elements to endanger national security".

According to the charge sheet, he is accused of conspiring with wanted national security suspect Nathan Law and other individuals between July 1, 2020, and November 23 that year to request foreign organisations and officials to impose sanctions, or blockade, or take hostile action against Hong Kong or the country.

Wong is also alleged to have asked foreign organisations and officials to seriously obstruct the formulation and implementation of laws and policies by SAR or central authorities.

National security police, in a separate statement, said officers arrested a man on suspicion of conspiracy to collude with foreign forces as well as "dealing with property known or believed to represent proceeds of an indictable offence" under the Organised and Serious Crimes Ordinance.