Chinese leader-in-waiting Xi Jinping has reappeared in public following an unexplained two-week absence.
His impromptu speech on Saturday ended an absence that had sparked rumours about his health and raised questions about the stability of the country's succession process.
In a brief English-language report that broke the official silence on his whereabouts, the Xinhua news agency said the vice-president arrived at China Agricultural University in the morning for activities to mark National Science Popularisation Day.
A picture on the government's website showed a healthy-looking Xi, with a slight smile and wearing a black informal jacket over a white shirt, walking around the university. A second picture, from Xinhua, showed a relaxed, laughing and gesticulating Xi inspecting some ears of corn.
Sources said Xi hurt his back while swimming earlier this month and that he had been obeying doctors' orders to get bed rest and undergo physiotherapy. Xi had not been seen publicly since 1 September, when he made a speech at the ruling Communist party's official training academy.
Since then, he has cancelled meetings with visiting foreign dignitaries including the US secretary of state, Hillary Clinton; the Singapore prime minister, Lee Hsien Loong; and the Danish prime minister, Helle Thorning-Schmidt. The Chinese government has yet to explain Xi's public absence.
Speculation over Xi's absence highlights the scrutiny China's succession process is under, tempered with uneasiness about the country's opaque political system, which often seems at odds with its rising global importance. "The leadership needs to realise how the world perceives this. They may have their own reasons for keeping secret, but it is not beneficial to China's global status and position as a world power," said David Zweig, an expert on Chinese politics at Hong Kong University of Science and Technology.
Xinhua said Xi, while visiting the university, spoke about food safety and made an impromptu speech in which he praised the university for sharing science with the public.
Xi is due to take over as head of the Communist party at a leadership congress this year, the first step in a generational power transition that will see him assume the presidency next spring, embarking on what is expected to be a decade at the helm of the world's most populous nation.