About 3,000 people braved the hottest day of the year so far and rival protesters on a march to mark the 25th anniversary of the Tiananmen Square crackdown.
Lee Cheuk-yan, chairman of the Alliance in Support of Patriotic Democratic Movements in China, which organised yesterday's event, said he was "very satisfied" with the turnout - double the 1,600 who marched last year.
But police said only 1,900 turned up, far below the 8,000 who took to the streets in 2009 to mark the 20th anniversary.
Video: Thousands of Hongkongers march in memory of June 4
At 1.30pm, the temperature at the Observatory in Tsim Sha Tsui was 33.2 degrees Celsius, the hottest this year.
"Hongkongers see the June 4 vigil as more important than the march so I think they will still come out on Wednesday to remember June 4," Lee said. He predicted more than 150,000 would gather in Victoria Park.
That was the attendance a year ago when the vigil was cut short by torrential rain.
The marchers left Victoria Park in Causeway Bay at 3pm yesterday and reached government headquarters in Admiralty two hours later, calling for the 1989 pro-democracy movement to be vindicated.
During the march, at Southorn Playground in Wan Chai, a war of words erupted with activists from the pro-Beijing "6.4 Truth" campaign, which argues that the crackdown in 1989 was "reasonable".
The two sides exchanged insults before police stepped in to calm things down.
Choi Suk-fong, a former journalist who witnessed the killings in Tiananmen Square, said activists who defended Beijing were "hurting the victims' families a second time".
Those calling for justice included teacher Tam Wai-pang, who brought his two-year-old daughter on the march.
"I wanted her to feel the atmosphere and I wanted to pass on the message to my next generation," Tam said.
Tam said he would also be at Wednesday's candlelight vigil.
This year the alliance has faced challenges from both sides of the political spectrum.
Independent pan-democrat lawmaker Wong Yuk-man will co-host a rally in Tsim Sha Tsui at the same time as the vigil in Victoria Park - hoping to attract 3,000 people.
Wong has derided the alliance's event as being too "ceremonial", while the alliance has hit back, saying the vigil is a "solemn ceremony".
Victor Wong Yu-cheung, a first-year history student at Chinese University, sided with the alliance. "The event has always been held at Victoria Park, so it doesn't make sense to hold something elsewhere," he said.
Wong said the debate about political reform had raised his awareness about democracy and prompted him to join the march for the first time.
As the rally ended, about 200 people, including League of Social Democrats' lawmaker "Long Hair" Leung Kwok-hung and members of student group Scholarism, marched to the central government's liaison office in Sai Wan, where police refused to admit their mock army tank.
There was a heavy police presence and protesters were only allowed to "pass by" the office gates in groups of 20 to 30.
"If you think this toy tank is dangerous, then you [police] are more immature than kindergarten students … the only thing dangerous is the Communist Party," said retired teacher Hon Lin-shan. "Police have a responsibility to serve the people."
He then asked members of Scholarism to immediately "take to Facebook" to recruit more protesters to the scene.
Repeated warnings not to throw objects over the gates were ignored by protesters as they tossed white chrysanthemums and paper "hell" money into the courtyard.
Leung, flanked by other league members, carried a blue coffin to the entrance of the office, chanting "the people will not forget".
On the other side of police lines, a crying woman argued with officers as she tried to burn joss sticks in front of the gate and make offerings for those killed in Tiananmen Square.
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