It's been 34 years since government troops opened fire on protesters in Beijing - estimates of the number killed range from several hundred into the thousands.

The arrests happened near Hong Kong's Victoria Park, with police saying some of the protesters displayed "items loaded with seditious wordings" - as well as "chanting and committing unlawful acts".

Among those detained was artist Sanmu Chan, who chanted "do not forget June 4. Hongkongers don't be scared!" as he was dragged away.

China has tightened its grip on Hong Kong in recent years following mass pro-democracy protests in 2019, with new laws on protests and pro-Beijing politicians installed.

Hong Kong was meant to retain much its freedoms under the 'one country, two systems' principle when the UK handed it back to China in 1997.

Ahead of this year's anniversary, the public broadcaster said around 6,000 police were on the streets.

Police said they were "highly concerned" about attempts "to incite and provoke others to commit illegal acts that endanger national security, public order and public safety".

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It was a different scene in Beijing at the site of Tiananmen Square, where tourists taking photos were watched by police and officials.

Most mention of the massacre is taboo, and the topic is heavily censored for internet users in the country .

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

When asked about global plans to mark the anniversary, foreign ministry spokeswoman Mao Ning said the government had already "come to a clear conclusion about the political turmoil in the late 1980s".

Taiwan is the only place in the Chinese-speaking world where the massacre can be discussed freely and activists will hold a memorial at Liberty Square.

Vice President William Lai, who will run for president next year, wrote on Facebook: "The event commemorating June 4 has continued to be held in Taipei, which shows that democracy and authoritarianism are the biggest differences between Taiwan and China."