Hong Kong authorities on Friday charged pro-democracy activist Joshua Wong with organising an illegal protest as they tighten a clampdown on unrest that has plunged the Asian financial hub into its biggest political crisis in more than two decades.

Wong, who led pro-democracy demonstrations five years ago that foreshadowed the latest turbulence, is the most prominent activist to be arrested since protests escalated in mid-June over fears China is exerting greater control over the city.

Police arrested several other activists and blocked plans for a mass demonstration on Saturday, in a show of force a day before the fifth anniversary of China’s decision to rule out universal suffrage in the former British colony.

The bespectacled Wong, who was 17 when he became the face of the student-led Umbrella Movement, as the 2014 pro-democracy protests were called, has not been a prominent figure in the latest protests, which have no identifiable leaders.

He was released from jail in June after serving a five-week term for contempt of court.

Wong and fellow activist Agnes Chow were charged with unlawfully organising a public meeting outside police headquarters on June 21. They were released on bail and the case was adjourned until November 8.

“Two months ago I served all of my jail sentence and left prison. Unfortunately, under the chilling effects generated by Beijing and Hong Kong governments, we are strongly aware how they arrest activists no matter whether they behave progressively or moderately,” he told reporters.

“All we ask for is just to urge Beijing and Hong Kong governments to withdraw the bill, stop police brutality and respond to our calls for a free election.”

Thousands of demonstrators blockaded police headquarters on June 21 protesting against a now-suspended extradition bill that would have allowed people to be sent to mainland China for trial in Communist Party-controlled courts.

More than three months of unrest has evolved into calls for greater democracy under the “one country, two systems” formula, by which Hong Kong has been ruled since 1997, guaranteeing freedoms not enjoyed on the mainland.

Protesters are riled by perceived interference by China that undermines that formula. China denies the accusation.

It has also accused foreign powers, particularly the US and Britain, of fomenting the demonstrations and warned against foreign interference.

Andy Chan, a founder of the pro-independence Hong Kong National Party that was banned last September, was arrested at Hong Kong airport on Thursday on suspicion of participating in riots and attacking police, police said.

Wong’s pro-democracy group, Demosisto, said the arrests were an attempt to scapegoat individuals in a movement that has built momentum without public figureheads. “The arrests were apparently a political operation,” Demosisto said on its Facebook page. “It will only make the government misjudge the public.”