Anti-extradition protesters again surrounded the Ma On Shan police station late on Friday night, where suspects arrested in a raid on an industrial building in Fo Tan are being held.
A small group of protesters sprayed graffiti and pointed laser lights towards the complex, demanding the release of seven men and one woman arrested on Thursday on suspicion of possessing offensive weapons.
The arrested included Chan Ho-tin, founder of the banned pro-independence group the Hong Kong National Party.
Police in riot gear dispersed the crowd. At least five shots were heard and people on a bridge nearby reported a pungent smell from the weapon police used, which is thought to be a kind of pepper bomb.
Some members of the public returned to the station offering so-called "hell money" to curse the officers inside and demanding to file a complaint over the behaviour of the police involved in the clearance.