HONG KONG -- Tensions are running high in Hong Kong as authorities scurry to conceal signs of dissent on the anniversary of the 1989 crackdown against student and civilian protesters in Beijing's Tiananmen Square.

Images of candles, rebellious graffiti and old news clips about the Tiananmen protests turned up across the city on Friday. But officials moved swiftly to cover messages they deemed sensitive with smears of paint or drop cloths, following on their refusal to allow an annual candlelight vigil to proceed in the city's Victoria Park.

Chow Hang-tung, vice chair of vigil organizer Hong Kong Alliance in Support of Patriotic Democratic Movements of China, was arrested Friday morning on suspicion of promoting an unauthorized assembly.

The 36-year-old barrister had told reporters that although the alliance had called off the vigil, she would light a candle at the park on her own, despite the high risk of arrest. A friend said after she was detained that Chow would fast unless she is allowed to light a candle.

A police spokesman said Friday that Chow and a 20-year-old deliveryman had been detained due to signs they had appealed online for people to go to the park despite the vigil ban. If convicted of inciting others to join an unauthorized assembly, they could be sentenced to up to five years in prison.

About 7,000 police officers were expected to fan out in the financial hub to stop any evening gatherings. Anyone wearing black clothing near Victoria Park would be considered "highly suspicious," according to local media reports.

This is the second year in a row in which Hong Kong has banned the Tiananmen commemoration, citing COVID-19 social distancing restrictions even though the city has not recorded any untraceable local cases in over a month.

Last June 4, tens of thousands defied the police ban to attend the peaceful gathering. But the new national security law Beijing imposed on the city almost four weeks later, which carries maximum penalties of life imprisonment for subversion and other new crimes, has muzzled many of the city's opposition voices.

Pro-democracy activist Joshua Wong last month was sentenced to 10 months in prison for joining last year's unauthorized observance.

Three other defendants who pled guilty in the case received sentences of four to six months. Another 20 people, including Apple Daily publisher Jimmy Lai and leaders of the Hong Kong Alliance, still face trial in the case.

Rally participants usually have chanted demands for China to "end one-party rule." With the country due to officially mark the 100th anniversary of the founding of the Communist Party on July 1, pro-Beijing officials have warned that such chants could violate the security law.

"The ban on the vigil is ridiculous. What has been going on for the past 30 years has suddenly become illegal," Albert Ho, a former lawmaker and longtime organizer of the event, told Nikkei Asia a few days before he was jailed on a charge related to another protest.

Ho said that he would commemorate the event in custody but urged the public to be "wise and flexible" to avoid legal risks.

"The most important thing is to pass on the truth about June 4," he said. "We shall never forget what happened."

Wu Lihong, a member of the Tiananmen Mothers Movement which brings together family members who lost loved ones in the 1989 incident, published a message online Thursday demanding Beijing conduct a thorough review of the crackdown and compensate victims' relatives. She urged China to hold officials accountable for the bloodshed.

A student photographs fliers about June 4 at a Chinese University of Hong Kong bulletin board.  (Photo by Cora Zhu)

The words of Wu, who lost her 35-year-old husband then, were originally supposed to be heard in Victoria Park in a prerecorded video Friday evening, as in past years. In 2019, the last approved vigil drew over 300,000 people.

In Wu's message, she thanked the citizens of Hong Kong for their persistent support and said she was thankful for friends committed to "respecting lives, ardently loving peace and standing against killings."

Meanwhile, Hong Kong's June 4th Museum was forced to close earlier this week after government inspectors declared its operations to be illegal, since it lacks a public entertainment license.

Despite the pressure, Hong Kongers are finding creative alternatives to remember Tiananmen, with artists and activists paying floral tributes, holding street performances and urging residents to turn on their mobile phone flashlights when dusk arrives.

Flyers calling for residents to "Never forget June 4" and to turn their lights on Friday evening to memorialize the Tiananmen victims sprung up furtively in urban neighborhoods like Mong Kok as well as the Chinese University of Hong Kong campus. Students approached there avoided comment on the anniversary.

A number of churches will hold special services to mourn those who died in the 1989 crackdown, defying attacks by pro-Beijing groups calling them "cults" and accusing them of "inciting chaos in the name of religious rituals."

Highlighting the authorities' increased sensitivity around Tiananmen, a public school teacher recently had his certification permanently revoked after he reportedly initiated a class discussion of the 1989 events.

"To be honest, I don't know how I can teach my students this part of history anymore," said a secondary school teacher. "You never know if anyone in the class, or their parents, will report on you."

Yaqiu Wang, China researcher at Human Rights Watch, said Friday, "The human rights situation has significantly deteriorated since President Xi Jinping came to power."

"The vigil ban really shows how much the Hong Kong human rights environment has deteriorated," she said. "Now the Hong Kong government has effectively banned protests, regardless what the protests are about. Just two years ago, millions of people were on the street protesting. Now, no one can."

Taiwan President Tsai Ing-wen said in a statement on Facebook that Taiwanese "will also not forget about the young people who sacrificed themselves on Tiananmen Square on this day 32 years ago," noting Hong Kong's traditional candlelight observance.

Gen. Kenneth Wilsbach, U.S. Pacific Air Force commander, told reporters at an online press briefing on Friday, "There's no surprise to suppress the discussion and commemoration of Tiananmen Square [crackdown] because that's another example of Chinese Communist Party overplaying their hands and completely looking past human rights."

Beijing officials however have stuck to their version of the 1989 incident. Without referencing Tiananmen explicitly, Foreign Ministry spokesman Wang Wenbin described the events Thursday as "those winds and waves that happened in the end of the 1980s" and said that China's actions were "completely correct."

Additional reporting by Stella Wong and Cora Zhu