Zhao, who resisted then paramount leader Deng Xiaoping's decision to crush the Tiananmen protests, has remained a politically sensitive figure for 15 years amid government fears his death could spark a groundswell of protest.
He was taken to hospital on 5 December for chronic pneumonia and had been in a coma since Friday after strokes.
"He died at 7.01am (2301 GMT Sunday). The medical report is not out yet," Zhao's son, Liang Fang, who adopted his mother's surname, told reporters.
"National leaders came to pay respects but it is not convenient to say who they are," said Liang.
'Free at last'
Zhao's daughter, Wang Yannan, who changed her surname after her father was purged, said he died peacefully.
Zhao was seen by some as a key
architect of China's reform
"He is free at last," Wang said in a statement to the media. Xinhua news agency confirmed his death in a brief report.
"Comrade Zhao had long suffered from multiple diseases affecting his respiratory and cardiovascular systems and had been hospitalised for medical treatment several times," it said.
"His condition worsened recently and he passed away on Monday after failing to respond to all emergency treatment."
Market reaction was muted, with China bourses falling not on Zhao's death but on a massive new power company listing and Hong Kong shares following Wall Street higher.
But analysts said investors would be on guard for political fallout.
The government stepped up security in Tiananmen once Zhao's health began to deteriorate, fearing his death could serve as a rallying point for reformers, workers bitter at high unemployment and poor farmers envious of wealthier
history will eventually give him a fair judgment"
But the square was quiet on a wintry Monday morning, with a scattering of tourists, Beijing residents and guards.
While Zhao is associated with opposition to the crackdown, his legacy remains unclear because the secretive Chinese leadership has never fully explained his role, Hou Dejian, a Taiwanese composer who staged a hunger strike in Tiananmen days before the crackdown, said in Taipei.
"There are so many things we don't know about, especially
the thinking behind the high-level officials at that time," Hou
"The only thing I can be sure of is Zhao Ziyang was more
sympathetic than other Chinese leaders at the time. I believe
history will eventually give him a fair judgment."
Security stepped up
Kenneth Lieberthal, University of Michigan professor of
political science, noted the new generation of college students and others in their 20s had no direct experience of Zhao and he was remembered among older generations as a political reformer.
"The leadership will take precautions anyway, with stepped up security and surveillance - they always do. But will this be a spark for another protest movement? I have no idea. But I would doubt that it would," Lieberthal said.
Zhao was placed under house arrest shortly before the army,
backed by tanks, crushed the demonstrations on 3-4 June, 1989. Hundreds of people were killed.
Zhao was last seen in public on 19 May 1989, when he appeared in the square and made a tearful appeal to the protesters to leave, saying he had come too late. The government declared martial law the next day.
He was accused of trying to split the party and sacked as general-secretary. Jiang Zemin took his place, ruling for more than a decade before handing over power to Hu Jintao in late 2002.