The ex-mayor of Beijing, said to have played a key role in the 1989 Tiananmen crackdown has died, as crowds in Hong Kong marked the protest's anniversary.
Chen Xitong died of cancer on Sunday, the Hong Kong China News Agency said. He was in his eighties.
Tens of thousands of people in Hong Kong staged a vigil on Tuesday, holding candles under umbrellas in the rain.
Hong Kong, a former British colony, is the only place in China to hold such public commemorations.
On the mainland, security for the anniversary was tight and activists were told to stay at home. Online searches of keywords like Tiananmen and Candle have been blocked.
Chen Xitong died on Sunday morning, reported the Hong Kong China News Agency, which is affiliated with the state-run China News Service.
It provided no further details.
Meanwhile, Chengdu-based writer He Sanwei also said he had been informed of the death of the former mayor by his relatives, according to the Associated Press news agency.
Chen Xitong is believed to have been a strong supporter of the military crackdown on the protest in Tiananmen.
However, he was quoted in a book published last year as saying he regretted the loss of life, adding that the crackdown was avoidable.
A native of the southern Sichuan province, Chen rose through the ranks of the Communist Party, becoming Beijing's mayor in 1983.
After the Tiananmen massacre, he was promoted to the country's all-powerful politburo.
But his meteoric rise came to an abrupt end in 1995 over a big corruption scandal. Three years later, Chen was sentenced to 16 years in prison, and was reportedly released on medical parole in 2006.
Some analysts think Chen's prosecution had as much to do with party infighting as with any wrongdoing.
The ex-Beijing mayor was once seen as a possible senior national leader in China. That - the analysts say - put him in direct competition with the then president, Jiang Zemin, who spearheaded a drive against corruption.
At the Hong Kong vigil, protesters demanded that Beijing withdraw its description of the pro-democracy movement as "counter-revolutionary".
"Vindicate June 4th!" many shouted. "Never give up!"
Organisers said 150,000 people had attended the vigil, but police put the number at 54,000.
The 1989 protests, which lasted for weeks before the violent suppression on 3-4 June, were led by students in Beijing but repeated in other cities.
The challenge to authority exposed divisions in the Communist Party leadership, but hardliners eventually prevailed.
Beijing has defended the decision to send in tanks and troops, but has yet to provide an official death toll. Estimates of the number of deaths range from the hundreds to the thousands.
The BBC's John Sudworth in Shanghai says the events that took place on Tiananmen square and the surrounding streets remain as taboo as they ever were - a reminder that there has been little if any political reform in the past 24 years.