Political observers say the rally will put more pressure on the central government to order a full investigation into Li's death, less than a month after the activist was found hanged from a hospital window in Shaoyang , Hunan province .

Post reporters interviewed 231 people during the rally, of whom 126 said Li's death had motivated them to join the annual march. About 60 per cent believed the rally could 'make a difference' to how the authorities handled Li's death.

Li was a veteran of the 1989 Tiananmen Square protests who spent 21 years in prison as a result of his pro-democracy activities. Li's sister, Li Wangling and some other family and friends who have spoken out about the case have been detained by police, placed under house arrest or gone missing.

Web designer Angus Ngan said the furore surrounding Li's death had motivated him to protest.

'I am using my conscience to safeguard our freedom,' he said. 'All this suppression of our freedom has gone well beyond my bottom line.'

Helen Ma Ching-chau, a retired civil servant in her 70s, said she had decided to march to show dissatisfaction at Beijing's handling of Li's death.

'I think the central government is using a delaying strategy,' she said.

And a 26-year-old visitor from Guangzhou, who declined to be named, said he hoped Hongkongers would voice demands for human rights to the central government, as discussion of dissidents was banned on the mainland.

Fong Chi-wah, a lecturer at Polytechnic University, said: 'Li was tortured for more than 20 years and now Beijing wants to cover up the truth of his death by detaining his family and friends. Hongkongers should voice their anger.'

Political scientists said the protests could put pressure on officials in Hong Kong and Beijing. 'The protest must put some pressure on the central government in dealing with the incident,' Professor James Sung Lap-kung, of City University, said. 'It will take time for the country's leaders to settle Hongkongers' nerves.'

He said the dissident's suspicious death had been a turning point in political activism for people from the city and the mainland, with many visitors from across the border joining yesterday's protest, taking advantage of a rare opportunity to pay tribute to a human rights activist.

'If the officials fail to handle the case well it will cause many more mainlanders to come to Hong Kong to voice their concerns,' Sung said.

Ivan Choy Chi-keung, of Chinese University, expects Beijing to pressure local officials to handle incidents involving activists more carefully in future after widespread coverage of Li's case in the Hong Kong and international media.

'The local officials will be advised to handle similar incidents with great caution,' he said. 'The incident has evolved into an international saga, which has embarrassed the central government a lot.'

Lawmaker Miriam Lau Kin-yee, chairwoman of the pro-Beijing Liberal Party, said mainland authorities must carry out a fair and upright investigation into Li's death. 'It must also be done in an effective and thorough manner,' she said.

Several of the city's delegates to the Chinese People's Political Consultative Conference earlier wrote to state leaders expressing Hongkongers' concerns about Li's death.

Two Hong Kong activists who paid a visit to Li's hometown were detained by Hunan police for hours on Friday before being escorted back to the city.

One of them said she had twice been forced to strip naked by officers, in what she believed was an attempt to humiliate her.