Tens of thousands of people across Hong Kong lit candles and chanted democracy slogans on Thursday to commemorate China's deadly Tiananmen crackdown, defying a ban against gathering as tensions seethed over a planned new security law.

The biggest crowds descended on Victoria Park that has hosted huge Tiananmen anniversary vigils for the past three decades, with smaller rallies erupting in multiple shopping districts and local neighbourhoods.

Graphic comparing police and organizer estimates for the turnout at Hong Kong's annual 1989 Tiananmen vigil. Hong Kong police on Monday banned the event for the first time in its 30 year history. Graphic comparing police and organizer estimates for the turnout at Hong Kong's annual 1989 Tiananmen vigil. Hong Kong police on Monday banned the event for the first time in its 30 year history. Photo: AFP / Laurence CHU

Police arrested some demonstrators in one shopping area, in scenes reminiscent of seven months of violent protests last year, although they allowed the main rally to proceed.

The displays of resistance came hours after Hong Kong's legislature passed a bill criminalising insults to China's national anthem, which the pro-democracy movement sees as yet another example of eroding freedoms.

Hong Kong's huge annual Tiananmen vigil has been banned this year because of the coronavirus Hong Kong's huge annual Tiananmen vigil has been banned this year because of the coronavirus Photo: AFP / ISAAC LAWRENCE

China also last month moved to impose the security law on Hong Kong which would outlaw subversion and has cemented fears that the semi-autonomous city is losing its treasured liberties.

"I've come here for the vigil for 30 years in memory of the victims of the June 4 crackdown, but this year it is more significant to me," a 74-year-old man who gave his surname as Yip told AFP as he joined the crowds inside Victoria Park.

People in 2019 attend a candlelight vigil at Victoria Park in Hong Kong to mark the Tiananmen crackdown anniversary People in 2019 attend a candlelight vigil at Victoria Park in Hong Kong to mark the Tiananmen crackdown anniversary Photo: AFP / Philip FONG

"Because Hong Kong is experiencing the same kind of repression from the same regime, just like what happened in Beijing."

Hundreds of people -- by some estimates more than a thousand -- were killed in on June 4, 1989, when China's communist rulers deployed the military into Beijing's Tiananmen Square to crush a student-led movement for democratic reforms.

A group of pro -emocracy activists hold a silent vigil before a protest outside the Chinese embassy in Tokyo to mark the 31st anniversary of the June 4, 1989 Tiananmen crackdown Photo: AFP / Philip FONG

Commemorations of the event are forbidden in mainland China but have been allowed in Hong Kong, which has been granted liberties under the terms of its 1997 handover from the British.

This year's vigil was banned, with authorities citing coronavirus restrictions on group gatherings even though people are allowed to commute in packed trains to work.

Placards and flowers are left in front on empty seats as pro-democracy legislators walk out of the chamber as debate continues in Hong Kong on June 4, 2020, ahead of a vote over a law that bans insulting China's national anthem Placards and flowers are left in front on empty seats as pro-democracy legislators walk out of the chamber as debate continues in Hong Kong on June 4, 2020, ahead of a vote over a law that bans insulting China's national anthem Photo: AFP / ISAAC LAWRENCE

As dusk fell on Thursday, many thousands of people, including prominent democracy leaders, began pouring into Victoria Park and lit candles as an act of remembrance and resistance.

Some wore black t-shirts with the word "Truth" emblazoned in white. Others were in office attire.

Hong Kong riot police set up a checkpoint near the Legislative Council on June 4 -- the 31st anniversary of the 1989 crackdown by Beijing on pro-democracy protesters in Tiananmen Square Photo: AFP / ISAAC LAWRENCE

Many shouted pro-democracy slogans including "Stand with Hong Kong" and "End one party rule", in reference to the communists who hold monopoly power in China.

students clean the Pillar of Shame, a statue by Danish artist Jens Galschiot to remember the victims of the 1989 Tiananmen crackdown students clean the Pillar of Shame, a statue by Danish artist Jens Galschiot to remember the victims of the 1989 Tiananmen crackdown Photo: AFP / DALE DE LA REY

Crowds have swelled at Hong Kong's Tiananmen vigils whenever fears have spiked that Beijing is prematurely stamping out the city's own freedoms, an issue that has dominated the finance hub for the past 12 months.

In response to the seven months of protests last year, China announced plans to impose the security law, which will be approved by national authorities in Beijing and bypass Hong Kong's legislature.

China says the law is needed to tackle "terrorism" and "separatism" in a restless city it now regards as a direct national security threat.

Critics, including many Western nations, fear it will bring mainland-style political oppression to a business hub.

In mainland China, authorities do not allow any open discussion about the Tiananmen crackdown and censors scrub any mention of it off the internet.

The candle emoji has been unavailable in recent days on China's Twitter-like Weibo platform.

Police in Beijing prevented an AFP photographer from entering Tiananmen Square to record the regular pre-dawn flag-raising ceremony on Thursday and ordered him to delete some photos.

The United States and Taiwan issued statements calling on China to atone for the deadly crackdown.

"Around the world, there are 365 days in a year. Yet in China, one of those days is purposely forgotten each year," Taiwan's President Tsai Ing-wen tweeted.

Secretary of State Mike Pompeo tweeted a photo of him meeting prominent Tiananmen survivors.

"The great achievements since the founding of new China over the past 70 or so years fully demonstrates that the developmental path China has chosen is completely correct," spokesman Zhao Lijian told reporters.