Xi Jinping, the Chinese vice-president, has appeared in public for the first time in a fortnight, in an apparent attempt to quash speculation that he is seriously ill or caught up in a power struggle that could threaten a smooth leadership transition in China.

Mr Xi, who is rumoured to have hurt his back while swimming, showed up on Saturday at an event to mark National Science Popularisation Day at China Agricultural University in Beijing.

The official Xinhua news agency published two photographs of the 59-year-old dressed in casual clothes, strolling with other officials. He was reported as saying: “Food safety is a significant livelihood issue,” at an exhibit showcasing instant tests for melamine in milk products. Excess melamine in Chinese infant formula sickened hundreds of thousands of children four years ago, and killed six.