Police say they arrested 228 people after a march by tens of thousands of protesters venting their frustration at Government policies and soaring property prices.
Organisers said up to 218,000 people took to the streets yesterday, the anniversary of the former British colony's return to China, to protest against a slew of issues, including a controversial plan to scrap byelections. Police estimated the crowd at 54,000.
Police said some protesters had refused to disperse from a road after the march ended and were detained for illegal assembly and causing obstruction in public places.
Television news footage showed police using pepper spray in attempts to disperse the demonstrators following a stand-off that lasted a few hours.
Some were later forcibly removed, handcuffed and carried into police trucks after scuffles with police.
"To restore peace and social order, as well as to guarantee public safety and to let the normal traffic resume, police decided to act and arrest the protesters in accordance with the law," the police said in a statement.
Such arrests are rare in Hong Kong, which was returned to Chinese rule in 1997 but retains a semi-autonomous status with civil liberties - including the right to protest - not enjoyed in mainland China.
Organisers have said the huge turnout at the rally, one of the biggest in recent years, was mainly due to a controversial Government proposal to scrap byelections if a seat is vacant and instead fill it based on previous results.
The proposal has been widely criticised by MPs and the legal professional body as infringing on voters' basic rights.
Analysts have warned that the current level of dissatisfaction with the Government is close to the levels in 2003, when a record 500,000 people took part in the annual pro-democracy march.
The unexpected show of people power at the 2003 march forced the Government to shelve a controversial national security bill and was a key factor that prompted the unpopular then-Chief Executive Tung Chee-hwa to step down the following year.