Hong Kong politicians pushing for a vindication of pro-democracy activists killed in Tiananmen Square have begun a North American tour, marking the 20th anniversary of the crackdown in Beijing. As part of their first major attempt to rally overseas activists to mark the event, they laid flowers at a Goddess of Democracy statue in San Francisco on Sunday remembering those killed by the People's Liberation Army. Szeto Wah, chairman of the Hong Kong Alliance in Support of Patriotic Democratic Movements in China, lamented one-party rule and said autocracy had led to the crackdown. He called on overseas activists to support the pro-democracy and human rights movements on the mainland, along with internet and environmental campaigns. Alliance vice-chairman Richard Tsoi Yiu-cheong said Hongkongers had not forgotten the crackdown, saying tens of thousands continued to attend the annual candle-light vigil held in Victoria Park. Mr Tsoi said the alliance would continue to fight for a reversal of Beijing's verdict on the crackdown, and would tell youngsters what happened. The event in San Francisco was attended by several prominent Tiananmen student leaders in exile, including Fang Zheng, who had his legs crushed by PLA armoured vehicles when troops drove protesters from the square. They were scheduled to speak on Hong Kong's political development at the University of California, Berkley, last night. The activists will visit Canada, Boston and New York, completing their tour on April 19 in Toronto, a city that has strongly supported their campaign.