This week's meeting between Russian President Vladimir Putin and Jiang Zemin was held at the initiative of the former Chinese president, apparently to show his political staying power, sources said.
Leaders from 33 countries gathered in Shanghai to discuss regional security, but it was the informal meeting between Putin and Jiang that set press rooms buzzing.
The pair met at a five-star hotel in downtown Shanghai - just hours after Putin's meeting with President Xi Jinping . The idea was first suggested by Jiang but Xi only approved it "very recently", one source said.
A spokesman for the Russian delegation said "the private meeting between old friends" lasted half an hour.
State media generally played down the encounter but the news spread via social media.
The official media's downplaying of the meeting indicates the leadership tried to keep it low profile, in contrast with Jiang's appointment with former US secretary of state Henry Kissinger last July.
That get-together was widely reported, highlighting Jiang's unreserved praise of Xi to his American guest.
A source said Jiang was eager to keep his political influence visible and Xi agreed - whether reluctantly or not - to give him a certain degree of public exposure via the meeting with Putin.
The meeting comes as Xi is pushing to expand his anticorruption campaign, which had put many former members of the political elite in the spotlight.
Jiang, 87, wanted to use the occasion to send a clear message to the world - "Look! I'm still alive and kicking", a source said.
Jiang arrived in Shanghai in mid-April for a private holiday.
"Few people knew Jiang's plan to meet Putin and the time and venue for the meeting were only confirmed very recently," one source said.
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