Three Hong Kong pro-democracy activists, including Joshua Wong who was one of the main leaders of the Umbrella Revolution in 2014, were arrested ahead of a proposed mass protest that has been banned by police, according to authorities on Friday.

Wong, pro-independence activist Agnes Chow and campaigner Andy Chan are seen as key figureheads of anti-government movements in Hong Kong over recent years, the South China Morning Post reported.

Wong and Chow were arrested for unlawful assembly in relation to the siege of police headquarters in Wan Chai by thousands of protesters on June 21, when demonstrators demanded a complete withdrawal of the now-shelved extradition bill and an exoneration of those arrested in previous clashes, police sources said.

Wong, who served time in jail for his role in the 2014 Occupy movement was detained early on Friday on his way to a metro station, according to the pro-democracy Demosisto party of which he is secretary-general.

A police source said Chow was arrested at her home in Tai Po.

Both are being held for questioning at police headquarters in Wan Chai.

Meanwhile, Chan was arrested on suspicion of rioting and assaulting a police officer on Thursday night after he was stopped from boarding a plane at the Hong Kong International Airport.

Early on Thursday, Hundreds of students in Hong Kong’s Chinese University turned what was billed as an orientation event for newcomers into an anti-government rally ahead of next weeks planned class boycott.

Last week, tens of thousands of people gathered on top of Hong Kong’s Lion Rock to shine lights across the city in solidarity with the city which has been shaken by anti-government protests for almost three months.

An estimated 210,000 people made a human chain across Hong Kong in the latest anti-government protest, whilst the outdoor community emulated the scenes on top of Lion Rock.

The city had appeared to have pulled back from a nosedive into violence, with the last serious clashes taking place a week and a half ago just after the city’s airport was paralysed by demonstrators.

On Sunday, at least 29 people have been detained for participating in a pro-democracy protest march in Hong Kong which led to violent clashes between police and the demonstrators.

The demonstrations were triggered by a controversial bill which would have allowed extraditions to mainland China, but have evolved into a call for wider democratic reforms and a halt to sliding freedoms.