Officers set up barricades around the park’s football pitches, basketball courts and the central lawn at noon, and large flags were put up, warning people they could be prosecuted for entering the area.
Dozens of officers were seen patrolling inside.
Senior superintendent Liauw Ka-kei said the police had made risk assessments and decided the park should be closed to ensure public order.
“Balancing all the situation, we decided that the best approach was to close Victoria Park… any person who enters or remains in the closed area is subject to a maximum penalty of 12 months [in prison],” Liauw said.
“I believe that the Hong Kong citizens will understand the decision made by the Hong Kong police in order to ensure public order, public safety, as well as balancing the rights of others. We are making the decisions to best protect members of the public.”
For the second year in a row, the authorities banned any handover day march, citing the pandemic. The force said allowing the march to go ahead would have posed a “grave threat” to the public and affected people’s rights.
Sources told RTHK that 10,000 police officers would be deployed on Thursday to stop people gathering on the streets.
In the morning, the League of Social Democrats staged a small protest in Wan Chai, as the government held its flag raising ceremony in the area.
Four members of the party, including chairman Raphael Wong and the wife of jailed activist Leung Kwok-hung, gathered at Southorn Centre.
They carried two red lanterns bearing the slogans “congratulations for the centenary anniversary” and “never forget your original intentions” – both addressed to the Chinese Communist Party.
The activists also had a banner calling for the release of political prisoners.
“Whether in Hong Kong or the mainland, the central government easily uses charges of subverting state power or colluding with foreign forces to subvert dissenting voices,” Wong said as he read out a statement.
Police officers checked the protesters’ belongings and kept a close eye on them throughout the short march to the Renaissance Hong Kong Harbour View Hotel.