The first official mention of missing leader-in-waiting Xi Jinping in nearly two weeks did little to dispel rumours about his health or ease uncertainty surrounding the Communist Party's leadership transition plans.

Reports by China News Service late on Wednesday and by the official Guangxi Daily yesterday said Vice-President Xi had expressed condolences to the family of a party veteran who died last week, along with party general secretary Hu Jintao and other leaders "through various means".

They were the first time Xi's name had been mentioned in the state media since he dropped out of public view 12 days ago. Analysts said the reports were clearly aimed at defusing swirling rumours about the mysterious disappearance of Hu's heir apparent ahead of the once-in-a-decade leadership shake-up.

But they said the reports failed to answer the main question on everyone's lips: where is Xi?

Foreign Ministry spokesman Hong Lei again refused to comment on rumours about Xi's health yesterday. He also remained silent about the date for the party's 18th national congress, which is expected some time next month.

But he insisted that preparations for the meeting, during which Xi, 59, is expected to take over as the country's top leader from 70-year-old Hu, were "well under way".

Zhang Lifan , a Beijing-based analyst, said the communist regime still treated its leaders' health problems as state secrets, but "the conspicuous disappearance of China's incoming leader has become an international topic and a potentially destabilising factor for the imminent party reshuffle".

While most rumours in the past week have said that Xi may be recovering from a minor health problem, such as a back injury suffered while swimming or playing football, unsettling speculation about more serious illnesses has begun to emerge over the past two days.

The Information Centre for Human Rights and Democracy said yesterday that Xi was diagnosed with early-stage liver cancer on September 2 during a regular check-up.