Tens of thousands of residents gathered in a Hong Kong Park on Thursday in memory of pro-democracy demonstrators crushed by tanks in Beijing's Tiananmen Square two decades ago.
The commemoration in semi-autonomous Hong Kong was the only major event marking the anniversary on Chinese soil.
The turnout was estimated by organisers 150,000 people, while Hong Kong police put the number 63,000. Hong Kong has been holding an annual vigil since 1990.
China blanketed Tiananmen Square with police and security forces on Thursday, blocking any attempt to commemorate the 20th anniversary of the deadly crackdown on mass democracy protests.
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 such as Yang Jianli and Xiang Xiaoji were turned away ahead of the anniversary.