Hundreds of people marched in Hong Kong on Sunday as the anniversary of the mass killings of student protesters in Beijing's Tiananmen Square.
British diplomatic cable released last year suggests more than ten thousand people may have been slaughtered in 1987.
Before then estimates of the number killed ranged from the hundreds to the thousands.
The protesters marched under the slogan "an end to one party dictatorship" ahead of an annual candle lit vigil.
"There should be an end to one party dictatorship in China .. most important is that we have the courage to continue to speak truth to power," said Albert Ho, Chairman of the Hong Kong Alliance in Support of Patriotic Democratic Movements in China.
They chanted slogans and held banners reading "Resist authoritarianism and commemorate June 4" amid a recent debate whether such calls may be deemed illegal.
The city's pro-Beijing camp has recently said calling and end to a "one-party dictatorship" is against the law and anyone doing so risks disqualification in the city's legislative council.