Police on Sunday said they arrested two men and a woman on suspicion of inciting others to intervene in the District Council elections.
The trio, aged between 31 and 67, were intercepted at Queen's Road Central near Pedder Street at around 8am.
Officers said the three are detained for further investigation.
Sources have said the suspects are members from the League of Social Democrats, including chairwoman Chan Po-ying.
Later in the day, the Independent Commission Against Corruption (ICAC) said it had arrested the trio picked up by police in Central for allegedly violating election laws by inciting others to boycott the polls.
"The case has been handed over to the ICAC for investigation," the anti-graft agency said.
"To ensure the election be conducted in a fair, just and clean manner, the ICAC, being the government department responsible for enforcing the [Elections (Corrupt and Illegal Conduct) Ordinance] will combat any conduct which might undermine and manipulate the election."