Updated

New rumors about health problems facing China's leader-in-waiting Xi Jinping swirled Thursday as the government continued to stonewall on commenting on his condition or whereabouts 12 days after he dropped from sight.

Official media mentioned Xi for the first time since his last appearance on Sept. 1, but the brief, obscure report failed to explain the extended absence that has sparked the rumors.

The reports said Xi, President Hu Jintao and other top officials had expressed their condolences "through various means" for the death of 102-year-old former general Huang Rong last week. The Guangxi Daily newspaper reported no other details. Identical reports were carried on the websites of the Communist Party and the official Xinhua News Agency.

China's vice president, Xi is due to take over as Communist Party head later this year and as president next year as the country transitions to a new generation of leaders. His prolonged and unexplained disappearance has sparked rumors and raised questions about the stability of the succession process.

For a fourth consecutive day, Foreign Ministry spokesman Hong Lei refused to offer any information on Xi.

Early rumors said Xi, 59, threw his back out swimming or pulled a muscle playing football. As the days passed, the speculation escalated to more serious conditions, including a heart attack, stroke, or emergency surgery.

And on Thursday, Hong Kong's Information Center for Human Rights and Democracy said a small cancerous growth had been discovered on Xi's liver on Sept. 2 and that he had undergone surgery to remove it this week at the elite military 301 Hospital in Beijing. The center said he was expected to reappear in public next week.

A man who answered the phone at the hospital's administrative office said he did not know whether Xi was being treated there. But he dismissed reports on Xi's condition as guesswork.

"I can say that these can definitely be only rumors. Information about the leaders' health is a big secret, known only to people at the highest levels," said the man, who refused to give his name because he wasn't authorized to speak to the media.

The silence on Xi isn't unusual, since China's top leaders live and work in isolation and information about leading personnel is only released after it has been carefully molded for positive effect. While the ruling party has become more sensitive to public opinion over nationalism and social unrest, it reverts to its roots as a clandestine organization when it comes to the leaders' private lives.

But the leader-in-waiting's sudden disappearance on the eve of his ascension comes during a year full of unforeseen political developments that had already threatened hopes for a smooth party leadership transition.

Most notably, the case of Bo Xilai, one of China's most charismatic and ambitious politicians who fell from power in March, remains unsettled. Bo's downfall sparked a dramatic scandal that led to his wife's conviction for murdering a British businessman.

If Xi's absence were to linger, it might also disrupt plans for the party congress — widely expected in late October — where Xi is to succeed Hu as party leader. The dates for the congress, held once every five years, were expected to be announced following a meeting of the 25-member Politburo this month, but it may be delayed if Xi remains out of action.

It isn't clear what would happen if Xi was indisposed for long. The party has never institutionalized its succession process, and the formula by which Xi was picked as Hu's successor five years ago remains a mystery to insiders.