Hong Kong used to play a leading global role in commemorating the 1989 crackdown by Chinese troops in and around Beijing's Tiananmen Square, in what was long seen as a symbol of the city's relative openness compared to mainland China.

Since Hong Kong's own major pro-democracy movement in 2019, however, China imposed a national security law and the latitude to commemorate June 4 has shrunk. Beijing says the law was necessary to restore stability after the demonstrations.

No public Tiananmen vigils have been held since 2020, while several sculptures on university campuses have been removed, and books on the events removed from public libraries.

The alliance that once organised the vigil has been disbanded following the arrests of several of their leaders in 2021.

This year, no local groups have applied to hold a public June 4 event, and at least four activists contacted by Reuters said they had been questioned by police about their plans.

Police said they "will make appropriate operational deployment in accordance with the threat to public safety, public order and national security."

Hong Kong's top security official on Monday warned people not to violate national security laws on "special occasions" when asked about the matter.

Some like Debby Chan, however, the owner of a grocery shop, said she would continue to give away "June 4" candles to her customers despite a visit to her shop by police officers over the past week.

"The commemoration of June 4th cannot be broken. It's a symbol of Hong Kong's civil society," Chan told Reuters.

Sum Wan-wah, the owner of a small, independent bookshop, said he still sells books such as "35th of May" by Hong Kong playwright Candace Chong, on an elderly couple contending with the killing of their son in the square.

"A lot of the books related to June 4 are no longer being published or are out of stock," said Sum, who set up a display of Tiananmen-related books and old newspaper clippings in a corner of his "Have a Nice Stay" bookshop.

"All this makes us try to spend time to preserve books that have disappeared from the public domain."

Another bookshop owner, Leticia Wong, who also displays Tiananmen-related books and sells copies of Chong's play, said she had been visited many times by government departments over the past week.

"No one said the books we sell are illegal, so I assume they're legal," said Wong, who runs the Hunter Bookstore.

The Fire Services Department said late on Friday night that "suspected unauthorised building works were noted inside the subject book store and the case was referred to the relevant department for follow-up action."

Derek Chu, who runs the "AsOne" online retail business, said he tried to organise a film screening on June 4 at a local cinema, but it was cancelled by the cinema.

Chu pledged to hand out candles instead.

"I won't give in to fear," he told Reuters.