Hong Kong police fired tear gas on February 29 to disperse hundreds of black-clad protesters, some armed with petrol bombs, during a rally to mark six months since the authorities stormed a subway station and arrested demonstrators.
The latest clashes are among the most violent to roil the Chinese-ruled city after a period of relative calm following intense anti-government protests that escalated in June last year, with fears over coronavirus keeping many residents indoors.
Hundreds of protesters gathered in and around Mong Kok district and the Prince Edward subway station, where some of the most fierce violence erupted on August 31, when police fired tear gas at pro-democracy protesters throwing petrol bombs.
Some chanted "Liberate Hong Kong, Revolution of our time," while others called for the police force to be disbanded, echoing slogans from previous demonstrations.
As the number of protesters increased, some set fires on Nathan Road in Kowloon district while others set up road blocks. Mong Kok subway station was closed.
The scenes brought back images of the clashes that plunged the city into turmoil last year and posed the gravest popular challenge to Chinese President Xi Jinping.
Many protesters are angry about what they see as creeping Chinese interference in Hong Kong, which returned to China in 1997 under a "one country, two systems" formula intended to guarantee freedoms that are not enjoyed on the mainland.
China says it is committed to the arrangement and denies meddling. It has accused foreign governments including the United States and Britain of inciting the unrest.
Protesters have called for an independent inquiry into the police force - one of five demands made on the Hong Kong government - amid allegations of excessive force.
Police say they have been restrained in the face of escalating violence.
The government announced in its budget this week that funding for the police force will reach HK$25.8 billion ($3.31 billion), up 25 percent from the previous year, drawing widespread criticism from democracy activists.
More than 7,000 people have been arrested in the anti-government protests, many on charges of illegal assembly or rioting, which carries a maximum sentence of 10 years.