China’s top leader-in-waiting Xi Jinping has not been seen in public for 10 days, sparking rumours that he is seriously ill.
The 59-year-old is expected to become president in March.
He was set to be named as the country’s next head of state at the forthcoming Communist Party Congress in October.
He made his last appearance at a school in Beijing on September 1st.
The Chinese government has declined to comment on Xi’s health or his whereabouts.
Unnamed officials quoted by the Reuters news agency said he hurt his back swimming.
But foreign media and social networking sites have carried unsourced reports suggesting that Xi’s condition is far more serious.
Speculation began last week when he skipped a meeting with US Secretary of State Hillary Clinton at the last minute.
The Chinese establishment has already been rocked this year when the wife of previous leadership favourite, Bo Xilai, was convicted of murder.