China's foreign ministry on Wednesday again refused to answer any questions about Xi Jinping, as concerns about the health of the country's likely next leader mounted.

Vice President Xi has not been seen in public for 12 days and has cancelled meetings with four foreign dignitaries, giving rise to intense speculation about his health and whereabouts, online and in overseas media.

China politics experts say he is likely suffering from a relatively minor health complaint, as anything more serious would have prevented President Hu Jintao from leaving the country to take part in last week's APEC summit.

But the government has so far given no explanation for Xi's absence from public view, refusing to answer repeated questions at a daily media briefing held by the foreign ministry.

"I have no information to offer you on this," ministry spokesman Hong Lei told reporters on Wednesday, echoing similar answers to questions concerning Xi in recent days.

Xi has been widely tipped to succeed President Hu as leader of the ruling Communist party at a crucial meeting that is expected to be held some time next month, before taking over as head of state in March.

His disappearance from public view has attracted global attention, but China's tightly controlled state-run media has completely ignored the issue, focusing instead on a row over Japan's purchase of the disputed Diaoyu islands.

Internet searches for Xi's name have been blocked in China, but users of Sina Weibo -- a popular microblog similar to Twitter -- have got around the restrictions by using such terms as "crown prince" and "she", a homonym for Xi.

"Our crown prince disappeared but we are concerned about the Diaoyu Islands," posted one.

Xi's last appearance in the state-controlled press was on September 1, when he made a speech at the Communist Party School in Beijing.

Since then he has cancelled planned talks with US Secretary of State Hillary Clinton and also missed meetings with the prime ministers of Singapore and Denmark and a Russian official.