Organisers of the annual June 4 vigil say they are expecting a huge turnout this year to mark the 30th anniversary of the 1989 Tiananmen crackdown.
The secretary for Hong Kong Alliance in Support of Patriotic Democratic Movements of China, Lee Cheuk-yan, said he believes the ongoing debate about changes to the city's extradition laws will motivate people to attend the event in Victoria Park.
"People want to express their views, their opposition, their aspiration for democracy," Lee said.
"We believe that this year there will be a turnout that will occupy the whole of Victoria Park, and Causeway Bay," he added.
On Friday, the police said crowd control measures and road closures around Victoria Park will start from 4pm this Tuesday.
The League of Social Democrats also say they have obtained approval for a march following the vigil to Beijing's Liaison Office in Western.