Japan's ambassador to Beijing has asked for more security for Japanese nationals in China after a 10-year-old Japanese boy was killed this week in a knife attack that was the second to target school students.

Some Japanese companies in China have offered to send their staff and their families back home after a 10-year-old Japanese boy was fatally stabbed in the Chinese city of Shenzhen, a Japanese executive and employees of Japanese firms in Beijing said on Friday.

Japan’s prime minister has demanded an explanation from Beijing over the fatal stabbing of a schoolboy in the second knife attack on Japanese children in China in recent months. The 10-year-old boy was stabbed by a man on his way to class Wednesday about 200 meters (650 feet) from the gates of the Japanese school in the southern city of Shenzhen,

In a call with China’s vice-foreign minister Sun Weidong on Thursday, Japan’s ambassador Kenji Kanasugi “strongly urged” Beijing to share detailed information about the incident, which was the second targeted attack on Japanese schoolchildren in China in recent months.

The killing of a Japanese schoolboy in the Chinese city of Shenzhen has sparked worry among Japanese expats living in China, with top firms warning their workers to be vigilant. Toshiba and Toyota have told their staff to take precautions against any possible violence,

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.

A 10-year-old student at a Japanese school in China died Thursday after being stabbed on the way to school the day before, Japanese officials said.