"Recent reports of some overseas media organisations about Jiang Zemin's death from illness are pure rumour," state-run Xinhua news agency on Thursday quoted authoritative sources as saying.
Speculation that the 84-year-old leader was seriously ill emerged when he failed to appear at celebrations marking the 90th anniversary of the Communist Party on July 1.
Reports on Wednesday said the Chinese government was censoring news about his death. Hong Kong's ATV claimed that Jiang had died, citing unspecified sources. Japanese daily Sankei Shimbun also reported on Thursday that Jiang had died in Beijing, quoting its sources.
Regarded as the most important leader after the CPC founder Mao Zedong and his successor Deng Xiaoping, who reversed several of Mao's policies, Jiang took over power in the aftermath of the 1989 Tiananmen square student protests.
Known as the "core" of the third generation Chinese leaders, Jiang carried on with Deng's policy of economic reforms in his 12-year-rule laying a strong foundation for China's economic development. He was succeeded by Hu Jintao both as President and CPC General Secretary.