Hundreds of people in Hong Kong have surrounded police headquarters, calling for an extradition bill to be scrapped.
Police have asked the protesters to withdraw peacefully, saying their presence would “seriously affect” emergency services.
Millions of people have marched against the bill in recent weeks, with violent clashes breaking out with police.
The bill, which allows extradition to mainland China, has already been suspended.
Critics say it would erode the judicial independence of Hong Kong.
Hong Kong has been part of China since 1997 under the “one country, two systems” principle, which allows it freedoms not seen on mainland China.
‘Face the people’
Early on Friday morning, a large group of protesters starting gathering outside the Legislative Council (LegCo).
The BBC’s Helier Cheung, who is at the scene, said the mood at that time was “relatively calm”.
But then prominent activist Joshua Wong called for people to march towards the police headquarters.
They began putting on face masks and started chanting for Hong Kong leader Carrie Lam to step down.
Wong, in a tweet on Friday, called for police to drop charges against people that had been arrested in earlier protests.
He also urged Hong Kong Police Commissioner Stephen Lo to “come down and face the people”.
Organisers estimate that millions in the city have taken to the streets over the past few weeks against the bill.
While the marches have been largely peaceful, some have descended into violent clashes between protesters and police.
One protest saw dozens injured after police tried to clear the protesters with tear gas and rubber bullets. Some 11 protesters were also initially arrested by police, though eight of them since been released.
The strong backlash prompted Hong Kong leader Carrie Lam to eventually suspend the bill. She issued a public apology and said it would not be revived until people’s fears were addressed.
Hong Kong protests: Hundreds surround police headquarters