The police's National Security Department on Wednesday said they arrested four men, aged 26 to 28, who are suspected of receiving funds to support people who have fled overseas and have continued to engage in activities that endanger national security.

The force said their investigation revealed the suspects had allegedly received money from "operating companies, social platforms and mobile applications". It's understood one of them is a former chairperson of the defunct group Demosisto, Ivan Lam.

"They were also suspected of repeatedly publishing posts with seditious intention on social media platforms, including content which provoked hatred towards the Central Authorities and the government of the Hong Kong Special Administrative Region, and advocated 'Hong Kong independence'," it said in a statement.

The force said officers had searched residences and offices, and seized documents and electronic communication devices.

They added the operation is ongoing and that the likelihood of further arrests has not been ruled out.