The deadly stabbing of a 10-year-old boy in China has raised alarm among the Japanese community in the country while triggering a flood of criticism of the incident and extreme nationalist comments on Chinese social media.

He was attacked by a 44-year-old man on his way to Guangzhou Japanese School in the south-eastern city of Shenzhen last Wednesday. 

The boy, who is the son of a Japanese father and Chinese mother, died from his injuries the next day.

Chinese authorities said the motive of the assailant remains unclear and the case was still under investigation.

It was the second attack on a Japanese national this year and took place on the 93rd anniversary of the Japanese invasion of Manchuria — a region of north-east China that today consists of the Liaoning, Jilin and Heilongjiang provinces.

After the attack on the 10-year-old, the Chinese ambassador in Tokyo was summoned by the Japanese Foreign Ministry where he was "strongly urged that security be strengthened including around Japanese schools throughout China".

Japan's Foreign Minister Yoko Kamikawa described the attack as "despicable" and asked her Chinese counterpart Wang Yi to "make every possible effort" to prevent further attacks on Japanese nationals in China.

She also urged Beijing to crack down on anti-Japan social media posts that could incite confrontation between Japan and China.

However, China's Foreign Ministry denied any link between the fatal incident to "anti-Japan sentiments" on Chinese social media.

"Let me reiterate that it's an individual case, and China is investigating and handling the case in accordance with the law," said ministry spokesperson Lin Jian.

But the stabbing has left the Japanese community in China on high alert.

The Japanese School of Beijing emailed parents with safety tips, such as not speaking Japanese loudly in public and warned against children leaving home alone.

Some Japanese companies are also reportedly allowing their expatriate employees in China to temporarily return home at the company's expense.

China ranks first in terms of the number of overseas bases of Japanese companies, according to Japan's Foreign Ministry, with some 31,000 firms represented in the $US19 trillion ($27.5 trillion) economy.

Polarised opinions on social media

While many netizens expressed sadness and shock at the stabbing of a child, some ultra-nationalists argued the attack was justified considering the atrocities committed during Japan's invasion of China during World War II.

Chinese authorities have been censoring all comments related to the incident and several major social media platforms including Weibo pledged to crack down on hate speech targeting Japanese people.

Some Chinese netizens commented that the country's patriotic education campaign had contributed to anti-Japanese sentiments.

Following the 1989 Tiananmen Square student protest, Beijing introduced compulsory patriotic education curriculum including the ideologies of key Communist Party leaders, the history of China and the party.

In Shenzhen, local residents laid flowers and notes of apology in front of the school of the deceased child.

"As Chinese people, we oppose this behaviour, we oppose teachings of hatred," said one man who identified himself as an ordinary Shenzhen resident.

Professor Florian Schneider, a China scholar from Leiden University, said the antagonistic and xenophobic sentiments were promoted by Chinese officials "in the service of patriotic education".

"Entire generations have grown up with nationalist interpretations that paint a bleak picture of Japan, and these impressions are perpetuated by museums, television entertainment, video games, and official commemoration activities," he said.

"Some of this is politically motivated, as nationalism helps paint a picture of a China that has shaken off a century of humiliation at the hands of foreign powers.

"While the vast majority of people in China are of course able to understand the nuances of their nation's history, there are bound to be individuals that draw simplistic and toxic conclusions."

Is Beijing's changing its attitude to nationalism? 

While the Chinese Communist Party had used nationalism to "bolster its legitimacy" in the past decades there were signs that its attitude was shifting, said associate professor Amy King, a China-Japan relations expert at Australian National University.

"I think the Xi Jinping government has toned down the patriotic education messages in many ways," she said.

But Professor Schneider said the Chinese government would likely "keep patriotism at play" while dialling back on the "nationalists and xenophobic elements of it". 

"I don't think the government is changing the tone fundamentally, they are too committed to the story," he said.

Dr King said authorities likely censored social media comments related to the stabbing in order to not undermine Japanese investment and tourism in China, and to avoid taking China-Japan relations back to the downturn of 2010-2016.

In the first half of 2010s, tensions between the two countries flared due to territorial disputes over Sensaku/Diaoyu islands, which sparked anti-Japanese demonstrations in more than 100 Chinese cities.

The bilateral ties eventually normalised in 2016, when China's President Xi Jinping and then-Japanese prime minister Shinzo Abe met at the G20 Leaders' Summit.

Need for 'education and open discussions'

Dai Yikun, a 23-year-old Shanghai resident who had previously lived in Japan, said he was against "radical nationalism" and violence, but that legitimate grievances toward Japan should be recognised.

"Many Chinese people have grievances towards Japan because of the difficult history — there is the feeling that many people in Japan don't really have much knowledge or acknowledgement of the country's past war crimes such as the Nanjing massacre," he said.

Some 14 million Chinese people died and 100 million more were made refugees following Japan's invasion and occupation during World War II, historians estimate.

But China and South Korea allege Japanese history textbooks — approved by the Japanese government — contain historical inaccuracies that downplayed or neglected to mention the country's war crimes during World War II.

Mr Dai said many people in his generation were very fond of "Japanese popular culture and sceneries", and that an increasing number of Chinese people were now studying and travelling in Japan today.

"We hope that the two countries can have more dialogues in the future," he said. 

Professor King said the challenge was that the reconciliation efforts, such as multiple apologies from Japanese leaders for World War II atrocities, were often undermined.

"We need more education and open discussions of the difficult and complex history between the two countries."