Joshua wong, one of hong kongs most high-profile pro-democracy campaigners, has been arrested as authorities crack down on protest leaders in the city.

The former leader of the now disbanded demosisto political group said he was detained and released on bail on thursday for allegedly participating in an unauthorised assembly last october. he also allegedly violated a law banning demonstrators from wearing masks.

This is the third case i need to face since last june when i left prison, mr wong said after he was bailed outside hong kongs central police station on thursday afternoon.

They can prosecute us, they can arrest us, they can lock us up in prison but they cant censor our commitment to fight for freedom. mr wong is expected to appear in court next wednesday.

His arrest is one of scores in hong kong since beijing in june imposed a national security law on the financial hub targeting those opposed to chinas increasing political control over the city.

The security law, which punishes crimes such as secession, subversion, terrorism and collusion with foreign forces with up to life imprisonment, is not supposed to be retrospective.

But since the law has come into place, hong kong police have stepped up arrests of high-profile pro-democracy figures, activists and politicians, despite some ceasing overt campaigning and disbanding their political parties.

Mr wong told the financial times in august that he expected to be jailed following the passage of the security law. his twitter account on thursday did not suggest he had been charged under the new law.

Another activist, agnes chow, a co-founder of mr wongs demosisto political group, and apple daily media tycoon jimmy lai were arrested last month.

Mr wong has previously faced charges over protests and was disqualified in july from standing in elections for the legislative council, the citys de facto parliament. the elections, which were scheduled for september, have since been postponed for a year.

Dixon ming sing, a political science professor at the hong kong university of science and technology, said: [the arrest] highlights the strong will of beijing to crack down on the local political opposition, which might not bode well for international financial capitals [willingness] to invest in hong kong.

Anti-government protests in hong kong first broke out early last year in opposition to an extradition law that would have allowed for the transfer of criminal suspects to mainland china for the first time.

The movement evolved into wider protests in support of the legal and political autonomy promised to hong kong after its handover by the uk to china in 1997.