Hong Kong police cited coronavirus restrictions to ban for a second year running an annual vigil to commemorate the Chinese Communist government's bloody crackdown on student-led pro-democracy protests in Beijing's Tiananmen Square in 1989.

Despite the ban, organizers expect a large turnout of people to mark the June 4 anniversary, though in small rather than big groups, like last year. Small online forums have called on people also to light candles to remember those who lost their lives in an episode that remains taboo in China.

"The mourning of 'June 4th' is a collective memory of Hong Kong people over the past 31 years," the Hong Kong Alliance in Support of Patriotic Democratic Movements of China said in a statement.

"The Alliance will continue to fight for the right of citizens to mourn the 'June 4th' lawfully," it said, adding that it had received a letter of objection from police due to coronavirus. It said it would appeal the decision.

International rights groups, Western governments and many in Hong Kong say Beijing is shifting the former British colony on to a more authoritarian path since it imposed a national security law on the city last June.

The security law combined with coronavirus restrictions have cleared the city's streets of protesters after anti-government demonstrations plunged the financial hub into turmoil in 2019.

The Tiananmen vigil in Hong Kong was banned last year for the first time in 30 years, with officials citing the curbs on movement to prevent the spread of the coronavirus.

Life in Hong Kong has largely returned to normal since the outbreak of COVID-19, with schools re-opened, most workers back in offices and restaurants and shopping malls full.

The government has still restricted outdoor gatherings to no more than four people, a move critics say is aimed at preventing any repeat of the 2019 protests.

This year, the anniversary is particularly awkward for Beijing, which is celebrating the 100th anniversary of the Communist Party.

When asked if commemorating the victims of Tiananmen would violate the new security law, Hong Kong leader Carrie Lam said in April it was important to show respect to the Party.

In previous years, tens of thousands have descended on the city's Victoria Park to light candles in a peaceful vigil to remember those who died in the violence in and around Tiananmen Square.

The death toll given by officials days after the crackdown was about 300, most of them soldiers, with only 23 students confirmed killed. China has never provided a full accounting of the violence, but rights groups and witnesses say the figure could run into the thousands.