Security Secretary John Lee, who signed the letters according to Reuters, previously announced that he was freezing bank accounts linked to the publisher of the city’s pro-democracy Apple Daily newspaper under Hong Kong’s sweeping national security law.

The letters were sent to HSBC Holdings Plc and Citigroup Inc earlier this month, Reuters reported.

Lee’s office didn’t immediately respond to calls and emails for comment on Thursday. An aide to Lai didn’t immediately respond to a request for comment.

A Citigroup spokesman said in an email that it doesn’t comment on individual accounts and is required to comply with all applicable laws and regulations in markets where it operates. A spokeswoman at HSBC declined to comment.

Lai, a prominent democracy activist who used his Next Digital Ltd media properties to support 2019 protests against China, is currently in jail for attending unauthorised rallies in Hong Kong. He also faces more serious charges under the security law, including “collusion” with foreign forces.

A financial adviser to Lai said the amount of money in the accounts was relatively small but represented the Hong Kong end of a network of international banking relationships related to his private wealth, Reuters reported.