Early on Wednesday protesters, some wearing face masks and helmets, blocked key roads around government buildings.
Police in riot gear responded by using pepper spray on protesters to disperse them and said they were prepared to use force.
The Legislative Council is set to debate the bill within hours.
Despite widespread opposition the government has said it will continue to push for extradition. A final vote is expected on 20 June where the pro-Beijing Legislative Council (LegCo) is expected to pass the bill.