Activist Joshua Wong has walked free from prison and vowed to join a mass protest movement demanding the city's Beijing-backed leader Carrie Lam steps down.
Wong's release on Monday comes as a political crisis in the Chinese-ruled city enters its second week, amid growing uncertainty over the fate of Lam and an extradition bill she postponed at the weekend after it triggered one of the most violent protests in decades.
"I will join to fight against this evil law," said Wong, 22, one of the leaders of the 2014 "Umbrella" pro-democracy protests that blocked major roads in Hong Kong for 79 days.
"I believe this is the time for her, Carrie Lam the liar, to step down."
The crisis escalated during Wong's five-week jail term for contempt of court.
Until this month, the failure of the Umbrella protests to wrest concessions from Beijing, coupled with prosecutions of at least 100 protesters, had discouraged many young people from going back out on the streets.
The upheaval comes at a delicate time for Chinese President Xi Jinping, who is grappling with a deepening US trade war, an ebbing economy and regional strategic tension.
Many residents of Hong Kong are increasingly unnerved by Beijing's tightening grip and what they see as the erosion of its freedoms.
Hong Kong has been governed under a "one country, two systems" formula since its return to Beijing, allowing freedoms not granted to the mainland, but short of a fully democratic vote.
Protest organisers said almost two million people turned out on Sunday to demand that Lam resign, while police said 338,000 participated in the rally.
Lam has apologised over her plans to push through the extradition bill that would allow people to be sent to mainland China to face trial.
Australian Associated Press