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.

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.

China's commerce minister said on Wednesday that Beijing will continue to negotiate "until the last minute" on the European Union's electric vehicle probe, with the investigation undermining confidence of Chinese companies investing in Europe.