Jiang Zemin, left, seen during his tenure as president of China, waves at well wishers as he arrives in Houston in 2002. (Richard Carson/REUTERS)

China’s media censors began blocking Internet search terms Wednesday to try to tamp down speculation on the health of ailing former leader Jiang Zemin. On Thursday, the official news agency denied reports on his death as “pure rumor.”

Speculation has been rife on microblogging sites that Jiang, 84, was dying or had died after he failed to appear Friday alongside other top leaders for ceremonies marking the 90th anniversary of the Chinese Communist Party’s founding. Jiang has been rumored for years to be in ill health.

On the most popular local Twitter-like microblogging site, Sina.com, searches were blocked for terms including “301,” the name of the Beijing military hospital where China’s top leaders are treated. Also blocked was Jiang’s name, which means “river” in Chinese, as well as “brain death” and “brain dead.”

Savvy Internet users found ways around the restrictions by chatting using other common words for “river” to refer to Jiang.

At midday Thursday, Xinhua, the official Chinese government-run news agency, broke its silence on the growing speculation about Jiang and denied he had died. A brief item said: “Recent reports of some overseas media organizations about Jiang Zemin’s death from illness are ‘pure rumor’,” according to an unnamed source, the Xinhua report said.

Media outlets in Hong Kong and Japan on Thursday reported — without attribution to any source — that Jiang had died.

The long official silence on Jiang’s health is not unusual in a country where basic facts about senior officials are closely guarded secrets. But the explosive growth of the Internet in China, with millions of microblogging sites, or “weibo,” is challenging the Communist Party’s monopoly on information.

The blocking of the search terms suggested that leaders were aware of the speculation and were determined to try to control the timing and manner of any announcement about Jiang.

The current leadership might also be sensitive to how the public will react to an announcement of Jiang’s death.

Jiang, who took over as party secretary after the Tiananmen Square massacre of 1989, was viewed as a free-market economic reformer who reduced the state’s role in business, brought China into the World Trade Organization and improved relations with the United States.

As Communist Party chief in Shanghai, Jiang, a Soviet-trained electrical engineer, is also remembered for dealing with student protests there without bloodshed.

In 2005, when Zhao Ziyang, another popular former party secretary general, died, the leadership went into crisis mode trying to craft an official, low-key announcement to prevent Zhao’s death from reigniting a national debate over the Tiananmen Square massacre.

Fueling rumors about Jiang’s health Wednesday was a heavier-than-normal police presence outside the 301 Military Hospital.

Late Wednesday, the Web site of a Hong Kong TV station published what appeared to be a tribute to Jiang, without confirming whether he had died.

Jiang was last seen publicly in 2009 at ceremonies marking the 60th anniversary of the founding of the People’s Republic of China. Since he has been reported to be in ill health in recent years, his death would not be a surprise.

Still, reports of Jiang’s health come at a sensitive time, as China is preparing to transition to a new generation of leaders next year. Jiang was said to be the leader of one faction maneuvering behind the scenes to support his favored candidates for elevation to the ruling Standing Committee.

Staff researcher Zhang Jie in Beijing contributed to this report.