HONG KONG—Police arrested 511 people who refused to leave a street in the financial district Wednesday, a day after a huge crowd marched across the city to mark the anniversary of the city's handover to China by denouncing interference from Beijing and demanding democratic elections.

Those arrested were mostly students who had vowed to stay in the park in the city's Central district until 8 a.m. Police began clearing the park in the early morning hours and the last students were taken at that time after the crowd counted down to 8 a.m.

Some of those taken away by police shouted and struggled, while others walked or were carried silently. Police held signs over the crowd telling them to board police buses.

The protesters were arrested for unauthorized assembly and obstructing police officers, police said. None of the protesters has been formally charged.

Tuesday marked the 17th anniversary of the end of British colonial rule and the city's return to Chinese sovereignty, a public holiday that has become a day of protest. Demands for universal suffrage are growing while the public is increasingly concerned about Beijing's approach to the city, which was promised a high degree of autonomy after the handover.