An annual vigil commemorating the 1989 Tiananmen Square massacre will not take place in Hong Kong this year, after police refused organizers permission to hold a mass gathering during the coronavirus pandemic.

On June 4, 1989 Chinese troops cracked down on pro-democracy protesters around Beijing's Tiananmen Square. No official death toll has ever been released, but rights groups estimate hundreds, if not thousands were killed.

The massacre made headlines around the world -- with iconic images such as the "Tank Man" bravely defying the troops on the square -- but it particularly resonated in Hong Kong, which was then eight years away from being handed over from British to Chinese control.

Hong Kong is the only place on Chinese soil where major mass commemorations are held for the event. Candlelit vigils have been held in Hong Kong's Victoria Park every year since 1990, and recent events have attracted tens of thousands of participants.

Police would not give permission for this year's rally to go ahead, however, citing coronavirus restrictions on gatherings of more than eight people, according to an official letter shared with CNN.