China's official media said Thursday that reports claiming former president Jiang Zemin had died were "pure rumour", after days of intense speculation about his health.

The state-run Xinhua news agency quoted "authoritative sources" in its report denying the rumour, which emerged last Friday after the 84-year-old failed to appear at celebrations marking the Communist Party's 90th birthday.

Speculation gathered momentum this week and culminated with Hong Kong and Japanese media putting out reports confirming his death.

Hong Kong broadcaster ATV announced Wednesday that the former president had died, citing unspecified sources and giving no details. It said it would air a special one-hour programme on Jiang but later cancelled it.

The Japanese daily Sankei Shimbun also reported Thursday that Jiang had died in Beijing, quoting "a source involved in Japan-China relations".

The Xinhua dispatch gave no further details on the former leader's health. Foreign ministry spokesman Hong Lei, who was repeatedly asked about the issue at a briefing, refused to comment and referred reporters to the Xinhua story.

Then in an unusual twist, ATV withdrew its news report and made a public apology "to the audience, Jiang Zemin and his family" in a brief statement.

Rumours have surfaced in the past that Jiang, who reportedly still wields a lot of power in the inner party sanctum, may be seriously ill.

His absence from the Friday gala in central Beijing was conspicuous as many other retired party and national leaders -- including former prime ministers Li Peng and Zhu Rongji -- were present.

On Thursday, searches for his name and other terms such as "cardiac arrest" -- one of his rumoured causes of death -- on the popular Twitter-like Weibo service were blocked, an indication that censors were barring information.

China routinely censors online content it deems politically sensitive. This includes the health of leaders, which is considered a state secret, apparently due to concerns illness might affect the appearance of stability in the party.

Even the word "river" -- the meaning of Jiang's surname -- was barred Thursday on Weibo, which more than 100 million Chinese people use. Typing "Jiang Zemin died" on search engine yielded no results either.

Jiang was appointed head of the ruling Communist Party by late leader Deng Xiaoping following the crushing of the 1989 Tiananmen pro-democracy protests.

He stepped down as the country's president in 2003 after guiding the nation through more than a decade of blistering economic growth, marked by a lack of corresponding political reforms.

Jiang is part of the so-called "third generation" of Chinese Communist leaders, a more technocratic and professional ruling elite to follow the first two "generations" of national founder Mao Zedong and then Deng.

In an attempt to get around China's online police force on Thursday, netizens were using characters that sound the same as the ones that make up Jiang's name to discuss the rumour.

For instance, they were using a character pronounced "jiang" that means stiff -- in reference to a corpse -- and "ming", which sounds similar to the last character in Jiang's name and means the underworld.