Restrictions in Hong Kong have stifled what were once the biggest vigils marking the bloody crackdown by Chinese troops on pro-democracy demonstrators, with the unconfirmed death toll estimated at between the hundreds or thousands.

Commemorations are expected in at least 30 places in North America, Europe and Asia.

In a statement, police said four people had been arrested for seditious intent and four detained for “breaching public peace” near Victoria Park, where for years after 1989 activists and regular citizens gathered on the Tiananmen Square anniversary.

This year, authorities gave permission for pro-Beijing groups to hold a food carnival in part of the park, while sealing off other areas with barricades.

Hundreds of police conducted stop and search operations, and took scores of people away, including activist Alexandra Wong, 67, who carried a bouquet of flowers, and a man who held a copy of “35th of May”, a play on the Tiananmen crackdown.

Hong Kong activists say such police action is part of a broad campaign by China to crush dissent in the city that was promised continued freedoms for 50 years under a “one country, two systems” formula when former colonial power Britain handed it back in 1997.

Security is significantly tighter across Hong Kong this year, with up to 6000 police deployed, including riot and anti-terrorism officers, according to local media.

Senior officials have warned people to abide by the law, but have refused to clarify if such commemoration activities are illegal under a national security law China imposed on Hong Kong in 2020 after mass pro-democracy protests.

In Beijing, Tiananmen Square was thronged with tourists taking pictures under the watchful eyes of police and other personnel but with no obvious sign of stepped-up security.

A group of relatives called the Tiananmen Mothers said the anguish never ended.

“Though 34 years have passed, for us, family members of those killed, the pain of losing our loved ones in that one night has tormented us to this day,” the group said in a statement released by the New York-based watchdog Human Rights in China.

In mainland China, any mention of the Tiananmen Square crackdown – where troops opened fire on pro-democracy protesters, killing hundreds if not thousands, according to rights groups – is taboo and the subject is heavily censored.

Foreign Ministry spokeswoman Mao Ning, asked about the government’s response to events around the world to mark the anniversary, told a regular briefing in Beijing on Friday that the government had already “come to a clear conclusion about the political turmoil in the late 1980s”.

In democratically governed Taiwan, the only part of the Chinese-speaking world when the anniversary can be marked freely and openly, activists prepared a memorial at Taipei’s Liberty Square with flowers of mourning and a “Pillar of Shame” statue.

In Sydney, dozens of demonstrators rallied at the Town Hall, chanting “free Hong Kong”, while holding up yellow umbrellas and placards in remembrance of 1989.

-with AAP