Hong Kong police fired pepper balls in the central business district and arrested almost 360 people after protesters gathered in opposition to the national anthem and national security law.
Demonstrators chanted pro-democracy slogans in Causeway Bay and Central at lunchtime.
They also chanted “Hong Kong independence, the only way out” and “one nation, one Hong Kong.”
At least 50 young people were held by police outside Hysan Place mall in Causeway Bay.
They were held for over an hour before being marched onto a police bus.
Activists were also rounded up and kettled in Central, where police shot pepper ball rounds near D’Aguilar Street.
Dozens of young people were also detained and held outside Langham Place mall in Mong Kok – some of them in school uniform.
Police raised flags on Hong Kong Island warning that protesters were in breach of the law and they may use force and tear gas to disperse them.
Other protesters gathered in malls to chant slogans, whilst one group briefly occupied Nathan Road, Kowloon’s main thoroughfare.
“At around 1 PM, protestors occupied the carriageways in the vicinity of Pedder Street, Central, causing serious obstruction to traffic,” police said in a Facebook post.
“Police officers have repeatedly warned protestors to leave immediately. Officers are taking resolute action to enforce the law and using the minimum necessary force. Protestors are warned to stop road blockage, proceed to safe locations and leave as soon as possible.”
Earlier, police set up a heavy security presence around the government headquarters and legislature in Admiralty in anticipation of the demonstrations.
“It’s like a de facto curfew now,” pro-democracy activist Nathan Law said on Twitter. “I think the government has to understand why people are really angry.”
Amnesty International also condemned the police crackdown: “Today’s excessive and indiscriminate use of force by the police to disperse protesters once again exposes the authorities’ utter disregard for human rights on the streets of Hong Kong. Mass arrests in entirely peaceful assemblies show that the Hong Kong government is targeting anyone exercising their right to freedom of expression,” said Deputy Director for East and South East Asia Joshua Rosenzweig.
The force also said that at least 16 people aged between 16 and 40 had been arrested as of 11.30 am.
They were arrested on suspicion of possession of an offensive weapon, possession of instruments fit for unlawful purposes and dangerous driving.
There had been online calls for a general strike and encirclement of the legislature, to halt the passing of the proposed law which would criminalise insulting the national anthem March of the Volunteers, punishable by a fine of up to HK$50,000 and three years behind bars.
There has also been opposition to Beijing’s decision to directly insert national security laws into the annex of Hong Kong’s mini-constitution, bypassing the local legislature.
Critics have said the legislation – prohibiting secession, sedition and subversion – would signal the death of the city’s cherished freedoms.