Thousands of protesters in Hong Kong raised candles in the air and sang solemn songs Saturday to mark the 16th anniversary of China's bloody crackdown on pro-democracy demonstrations on Tiananmen Square (search), while security was tightened in Beijing to block any memorials there.

China's Communist Party has eased many of the social controls that spurred the 1989 student-led protests, which ended when soldiers and tanks attacked, killing hundreds of people. But Chinese leaders still crush any activity that they fear might challenge its monopoly on power.

Tiananmen Square was open to the public, but extra carloads of police watched tourists on the vast plaza and there was no public mention of the anniversary or any sign of attempts at commemorations.

In Hong Kong, people holding candles filled an area the size of five soccer fields at Victoria Park (search) — the only large-scale protest on Chinese soil. Police estimated that 22,000 people attended the annual vigil, but organizers said the crowd numbered 30,000 to 40,000.

Many residents of the former British colony remain emotional about the Tiananmen crackdown because it happened just a few years before the city returned to Chinese rule in 1997.

"My heart is heavy," said Shum Ming, 58, a construction worker. "Hong Kong people will not forget this history when a government uses guns and tanks to crush students. It's very atrocious."

Protester Henry Ho, 19, a Hong Kong University student, said, "If the Chinese government can say what happened that night and can say that they're sorry, it can show that they are not the same government from the past."

Many feel a duty to speak out because they have freedoms of speech and assembly that don't exist on the mainland. Hong Kong is ruled under a "one country, two systems" formula that allows the city a wide-degree of autonomy.

Banners and signs said, "Don't forget June 4" and "Democracy fighters live forever."

Vigil organizer Lee Cheuk-yan, vice chairman of the Hong Kong Alliance (search), said, "Our slogan is 'Recognize history' and we're asking Beijing to do just that."

But Donald Tsang, the front-runner campaigning to become Hong Kong's next leader, said China has made great strides in improving its economy and people's livelihood.

"I had shared Hong Kong people's passion and impetus when the June 4 incident happened. But after 16 years, I've seen our country's impressive economic and social development," Tsang said. "My feelings have become calmer."

A booming private economy has freed millions of Chinese from the structure of state jobs that controlled where they lived and worked — and even whom they could marry.

In their rare public comments about 1989, Chinese leaders defend the crackdown by pointing to the nation's emergence as an economic powerhouse since then, saying it would have been impossible without the enforced stability of one-party rule.

In Australia, a senior Chinese diplomat who abandoned his post and is seeking political asylum came out of hiding Saturday to speak at a Sydney rally to observe the anniversary.

Chen Yonglin, 37, the consul for political affairs at the Chinese Consulate in Sydney, said he was defecting because of a lack of freedoms in China.

"In 16 years, the Chinese government has done nothing for political reform," he said. "People have no political freedom, no human rights."

Chen claimed he still was being chased by Chinese security agents and feared they might kidnap him.

Neither Australia's foreign ministry nor the Chinese Embassy in Canberra could be reached for comment on Chen's statement.

The anniversary, always sensitive for communist leaders, is especially touchy this year because it follows the death in January of Zhao Ziyang, the former Communist Party boss who was purged in 1989 after sympathizing with the protesters.

A retired senior Chinese official, Li Pu, called on Beijing to vindicate the 1989 pro-democracy movement, which was branded a "counterrevolutionary riot" by the Communist leadership.

"The students made big mistakes, but the government's military crackdown was even worse. It was extremely wrong to send troops against ordinary people," Li, former vice president of China's official Xinhua News Agency and a friend of Zhao's, said in an interview with Hong Kong's government-owned radio RTHK.

"History will give Zhao Ziyang justice. Some years later, June 4 must be vindicated," he said in the radio program.