Former Chinese president Jiang Zemin has made a rare public appearance, state media reported Saturday, ahead of a pivotal Communist Party congress that will usher in a new generation of leaders.

The 86-year-old, still considered an influential figure within China's ruling party, was pictured meeting leaders of the Shanghai Ocean University in Beijing, the People's Daily website and other media reported.

Jiang and his wife Wang Yeping held a reception on October 9 for senior officials to celebrate the centenary of the university, which specialises in the marine environment and the fishing industry, the institution's website said.

The ex-leader told those present that "the 21st century is the century of the sea" and that "as a country with scarce natural resources, China must attach great importance to marine development", according to the site.

His comments came as China is locked in a dispute with Japan over an East China Sea island chain, which is administered by Tokyo but claimed by Beijing, and which is believed to sit atop valuable natural resources.

Jiang, who was president from 1993 to 2003, no longer has an official role but is believed to still exert influence behind the scenes.

His appearance came a month before the November 8 Communist Party congress, where it is expected that a new Politburo line-up will be unveiled, kicking off a once-in-a-decade leadership transition.

Speculation swirled last year that Jiang might be seriously ill and a Hong Kong TV channel was fined after erroneously reporting that he had died.