HONG KONG, June 30 (AFP) — Four young leaders of a Hong Kong pro-democracy political party announced their resignations on Monday, hours after Beijing passed a sweeping national security law for the city.

Joshua Wong, Nathan Law, Jeffrey Ngo and Agnes Chow said they were ending their involvement in Demosisto, a party that has infuriated Beijing by campaigning for universal suffrage and for foreign countries to sanction China for rights abuses.

All four said they would continue to campaign in a personal capacity, a move that suggests they might be hoping to shield Demosisto from being prosecuted or disqualified once the new security law comes in. 

"I will continue to defend my home — Hong Kong — until they mute me and eliminate me from this land," Wong wrote on Facebook.

Both Wong and Law — prominent figures from 2014's student-led democracy protests — are running for Hong Kong's Legislative Council election in September.

The city's partially-elected legislature is weighted to return a pro-Beijing majority.

But pro-democracy parties hope to snap up most of the chamber's electable seats, capitalising on growing public anger with Beijing's rule.

Campaigners like Wong — who has previously been jailed for his activism — are routinely villainised by China's state media as "separatists" even though Demosisto does not advocate independence.

Rights groups have expressed fears the new security law — which was passed by China's top lawmaking body on Tuesday morning — could be used to silence figures and parties that push for Hong Kong to have greater autonomy.

The precise wording of the new security law remains a secret but Beijing has said it will outlaw acts of subversion, secession, terrorism and colluding with foreign forces.

Similar national security laws are used on the authoritarian mainland to crush dissent, in particular the more vaguely worded subversion and collusion offences.

Beijing says the legislation is needed to return stability to Hong Kong after a year of pro-democracy protests.

It says only a small minority of people will be targeted, especially those promoting separatism.

On Sunday Wayne Chan, the leader of a small pro-independence group currently being prosecuted for taking part in unlawful assemblies, confirmed that he had jumped the bail and fled the city.