The Hong Kong government says it has cancelled the passports of six pro-democracy activists residing in Britain, saying they continue to engage in activities that endanger national security.

The government on Wednesday announced measures applied against "the relevant absconders." The activists are on a wanted list for inciting secession and other charges.

The measures were taken under a new security law that took effect in March. They include banning financial support for the activists.

Among the six is Nathan Law, a leader of the 2014 Umbrella Movement protest. He has continued to call for international support for the pro-democracy movement in Hong Kong after fleeing to Britain.

The territory's Security Secretary Chris Tang told reporters that the six have been sheltered in the UK and continue to collude with external forces to engage in activities that endanger national security.

Tang said the latest measures combat and deter such activities. He also said consideration will be continued to determine whether similar measures should be taken against others on the wanted list who fled overseas.

Law said on social media that he no longer uses a Hong Kong passport.