Absence of Chinese leader Xi Jinping fuels speculation about transition China's president-in-waiting, Xi Jinping, canceled a planned meeting in Beijing on Monday with the visiting Danish prime minister - his third no-show for a meeting with a foreign dignitary this month - fueling speculation that the country's carefully orchestrated leadership transition had run into more unexpected turbulence. Chinese government spokesmen offered no explanation for the latest cancellation or why Xi, who is vice president, has not appeared in public since Sept. Last week, Xi canceled a scheduled meeting with Secretary of State Hillary Rodham Clinton and another planned meeting with Singaporean Prime Minister Lee Hsien Loong. Unconfirmed reports at the time said Xi may have thrown out his back and was recuperating. The cancellation of the Clinton meeting was also seen as a possible snub, to show the Beijing leadership's pique with the Obama administration's China policies. But Monday's cancellation with Prime Minister Helle Thorning-Schmidt sparked a fresh round of speculation, with possible explanations for Xi's absence ranging from more serious health concerns to possible instability and intrigue at the very top of the Communist Party hierarchy. China's Communists are due to meet later this year to name a new president - widely expected to be Xi - and new members of the now nine-member Politburo Standing Committee that effectively runs the country. But remarkably, as of now, no date has been announced for the conclave. That has added to the sense that the behind-the-scenes jockeying remains intense and that not all is settled among the leadership's competing factions and personalities as they dole out the top positions. At the very least, Xi's disappearance from public view and the unofficial, conflicting accounts of his absence starkly illustrate the challenge facing China's Communist rulers as they try to stage-manage an anachronistically closed and secretive transition process for the first time in the age of microblogging and social media. Chinese leaders remain opaque and largely loathe even rudimentary forms of transparency - particularly when it comes to their health. But in the absence of real information, the microblogs have swiftly stepped into the void. "You see the tension, with elite politics not changing as fast as society is changing," said Cheng Li, an expert on China's leadership with the Brookings Institution in Washington. Now, he said, "there's a lack of transparency, so we end up with all these" rumors. The most oft-repeated speculation, which first surfaced on overseas media sites, was that the portly Xi threw out his back, either while swimming, playing soccer or, according to one version, playing golf. A more serious version of that rumor is that the vice president had a mild heart attack. Meanwhile, a Chinese-language Web site that often reports on the inner workings of the leadership - and has produced some accurate reports and even more wild misses - said Xi may have been targeted in a car accident by a military associate of deposed Politburo member Bo Xilai, whose wife, Gu Kailai, was recently convicted of murdering a British businessman. That report was later taken down.