HONG KONG - Clad in black or white, and cradling candles, Hong Kong residents transformed a park into a sea of flickering lights on Thursday, in memory of pro-democracy demonstrators crushed by tanks in Beijing's Tiananmen Square two decades ago.

A woman holds a candle as part of a candle light vigil in Victoria Park in Hong Kong on the 20th anniversary of Beijing's crackdown on pro-democracy protesters in Tiananmen Square. The leaders of the original protest appealed for democracy in China, voicing hope that change would come eventually. (AFP/Ed Jones) While China has tried to whitewash the incident over the past two decades and has tightened security around Tiananmen Square in recent days, Hong Kong has long made the most of its unique freedoms to openly challenge Beijing to reverse its verdict on June 4 and fully account for the killings.

The turnout was estimated at 150,000 people, organizers said, as crowds overspilled from six football pitches in a downtown Hong Kong park. The figure was even higher than in 1990 when the annual vigil first began, underscoring the anniversary's poignancy.

But Hong Kong police put the estimate at 63, 800.

"We will never forget June 4," the crowds chanted while singing remembrance songs, waving candles and linking arms.

Many in Hong Kong acknowledge China's economic progress since 1989, but still find the memories of June 4 impossible to forget.

"I know China is improving, but I hope that they will admit that they fired guns and did wrong," said Kong Choi-fung, a 44-year-old church worker who took her two children to the vigil.

A recent annual survey found a record 60 percent of Hong Kong people want China to reverse its official verdict on June 4.

ZHAO'S MEMOIRS

A British colony until 1997 when Hong Kong switched to Chinese rule, the city has enjoyed wide-ranging freedoms of expression denied most people in mainland China. But China has delayed calls for direct elections till 2017 at the earliest.

This year, painful memories have been accentuated in the city by political controversy and the symbolic 20th anniversary.

The memoirs of former Communist Party Chief Zhao Ziyang, who sided with the 1989 demonstrators, has been a publishing sensation, with some of his voice recordings played at the vigil.

The vigil also saw the rare appearance of a Chinese student leader from 1989, Xiong Yan, who was able to enter Hong Kong over the weekend. Other Chinese June 4 dissidents suh as Yang Jianli and Xiang Xiaoji were turned away ahead of the anniversary.

"Hong Kong is a part of China and can influence China more than any country, more than any place," said Xiong, who was one of 21 people placed on Beijing's "most wanted list" in 1989.

"I heard a lot of people came down from China tonight. They want to experience this. That's great ... where there is freedom, there is the meaning of life," he told Reuters.

(Additional reporting by Venus Wu; Editing by Sanjeev Miglani)