President Xi Jinping has overseen a surge in Chinese nationalism to boost his government’s popularity as tensions have frayed with rivals. Now, the murder of a Japanese boy is exposing the dangers of that tactic.

The attack on the 10-year-old boy was the second such incident in months amid a social-media campaign that has stirred up anti-Japan sentiment in China.

Japanese Prime Minister Fumio Kishida demanded an explanation from Beijing on Thursday about the fatal stabbing of a Japanese schoolboy in Shenzhen and urged China to ensure the safety of Japanese citizens.