Blindfolded protesters wearing white clothing were among 25,000 people who marched to the Central Government Liaison Office yesterday demanding an investigation into the death of blind-and-deaf activist Li Wangyang.
The rally was marred by scuffling outside the office when protesters smashed through a police barricade.
Western District police commander Rebecca Lam Hiu-tong said police used pepper spray on protesters, whom she described as irresponsible after they tried to remove metal barricades.
Traffic along Connaught Road West was affected as a number of the demonstrators forced their way into one of the lanes.
The protest followed media reports that the Shaoyang authorities had cremated Li's body despite opposition from his family.
Shaoyang officials insisted Li committed suicide.
Lawmaker Ip Kwok-him said he will write to the National People's Congress chairman to urge the central government to intervene. Ip, who a few days ago said such a move was unnecessary, said he changed his mind after reading news reports over the past few days.
However, at City Forum, Chinese People's Political Consultative Conference member Lew Mon-hung said it was unfair to lay the blame on Beijing as it was still uncertain whether Li's death was a suicide or a homicide.
Yesterday's protesters came from more than 30 groups, some wearing black and carrying white chrysanthemums, as they set off at 3.30pm from Chater Road.
"The truth has to be revealed. Li's family deserves justice," the protesters chanted.
They demanded that the central government step in to conduct a thorough probe. They also called on Chief Executive Donald Tsang Yam-kuen and Chief Executive-elect Leung Chun-ying to pass on their demands to Beijing.
Leung has repeatedly refused to comment on the case, saying it would not be suitable given his position.
Li was found dead in a Shaoyang city hospital ward on Wednesday, hanged from a window bar with a strip of cloth. His feet were touching the floor, raising suspicions about the suicide claim.
A 27-year-old liberal studies teacher, Lo Yat-ko, said he normally does not join such protests. But he felt the need this time because he was angry about what happened.
"This time someone actually died," Lo said. "The mainland authorities went further this time than just locking up activists in prison."
Another protester, Tsang Kwok-fung, a 40-year-old flight attendant, said since the chief executive-elect will not pass Hongkongers' demands to Beijing, the people have to make their voices heard by taking to the streets.
As the protesters arrived at the liaison office, police blocked them off, allowing only a small group to go to the entrance.
Police said 3,600 protesters set off from Central and the number rose to 5,400 in Western District as more people joined.