The semi-autonomous southern Chinese city has seen two months of unrest that was triggered by opposition to a planned extradition law but quickly evolved into a wider movement for democratic reforms.
Authorities in Hong Kong and Beijing this week signalled a hardening stance, including with the arrests of dozens of protesters, and the Chinese military described the unrest as "intolerable".
But more protests have been scheduled, starting on Friday evening, with members of Hong Kong's usually tight-lipped civil service due to hold a rally despite a government warning that they could be sacked for doing so.
"Any acts to undermine the principle of political neutrality of the civil service are totally unacceptable," the government said late on Thursday.
Medical workers have also called a rally for Friday evening and there are unsanctioned marches planned for Saturday and Sunday, as well as a city-wide strike on Monday.
Previous unsanctioned marches have quickly descended into violent clashes with police.
Independence activist arrested
Deepening tensions, police said eight people were arrested Thursday night on charges of possessing offensive weapons and explosives following a raid on an industrial building.
In an update on Friday, police said they found one petrol bomb and some smoke grenades.
A senior police source, who asked not to be named, told AFP that independence activist Andy Chan was among those detained and that a "gasoline bomb" was found on the premises.
Chan's small independence party was outlawed last year on the grounds it posed a national security threat, the first such ban since the former British colony returned to Chinese rule in 1997.
Chan's party contained only a few dozen members, but Beijing sees calls for independence as an absolute red line.
The banning of his party -- and the expulsion of a Financial Times journalist who chaired a talk with Chan at the city's press club before the party was outlawed -- were held up as two examples of eroded freedoms in Hong Kong.
Under the terms of the 1997 handover deal, the city has rights and liberties unseen on the mainland, including an independent judiciary and freedom of speech.
But many say those rights are being curtailed, citing the disappearance into mainland custody of dissident booksellers, the disqualification of prominent politicians and the jailing of pro-democracy protest leaders.
Surge in violence
Public anger has been compounded by rising inequality and the perception that the city's distinct language and culture are being threatened by ever-closer integration with the Chinese mainland.
The past two weekends have seen a surge in violence used by both protesters and police, who have repeatedly fired rubber bullets and tear gas to disperse projectile-throwing crowds.
A mob of pro-government thugs also attacked protesters, putting 45 people in hospital.
Hong Kong's police have increasingly adopted tougher tactics, including by this week charging 44 protesters with rioting -- an offence that carries up to 10 years in jail.
Hong Kong chief executive Carrie Lam has made few concessions beyond agreeing to suspend the extradition bill, and she has made few public appearances.
Protesters are demanding her resignation, an independent inquiry into police tactics, an amnesty for those arrested, a permanent withdrawal of the bill and the right to elect their leaders.
Pro-democracy protesters in Hong Kong are gearing up for more rallies starting on Friday, in defiance of a series of warnings from China and after a prominent independence campaigner was arrested.