China’s internet companies have announced a crackdown on “extreme nationalism” online, particularly anti-Japanese sentiment, after a Chinese woman was fatally stabbed while protecting a Japanese mother and child in Suzhou. Tencent and NetEase, two of the biggest firms, said at the weekend that they would be investigating and banning users who stirred up hatred. The notice from Tencent, which owns the messaging app WeChat, said the incident in Jiangsu province had “attracted public attention” and that “some netizens incited a confrontation between China and Japan [and] provoked extreme nationalism”. An unemployed man, surnamed Zhou, was arrested last week for stabbing a Japanese mother and child at a bus stop outside a Japanese school in Suzhou, a city in eastern China. Hu Youping, a Chinese woman who intervened in the knife attack, died from her injuries. Hu was praised for her heroism and bravery in online tributes and the Japanese flag was flown at half mast at Japan’s embassy in China, but in other quarters there was an extreme nationalist response. Weibo, a Twitter-like platform with 588 million monthly active users, said that after the knife attack some users had “published extreme remarks that incited nationalist sentiment, promoted group hatred and even cheered for criminal behaviour in the name of patriotism”. Douyin, a short-video app similar to TikTok, said it would investigate “extreme xenophobia” that appeared on certain accounts, including speculation about spies associated with Japanese schools in China. Nationalist sentiment, often expressed as hatred towards Japan, has thrived in recent years on the closely monitored Chinese internet, with little intervention from the authorities or from internet companies, which are quick to censor any content perceived as being critical of official government narratives. Videos mocking Japanese schools are particularly popular, with one skit online showing Chinese schoolchildren fighting back against racist Japanese educators. Many social media users drew a connection between the online xenophobia and real-life attacks after the Suzhou stabbing. “Random attacks happen randomly, but xenophobic social media videos that incite hatred against everyday people and businesses should be brought under control,” wrote one Weibo user, according to comments compiled by the US-based news site China Digital Times. Weibo said it had removed 759 pieces of illegal content while Tencent said it had dealt with 836 posts that it said violated its rules. Both platforms said they had blocked several accounts. Some people were dissatisfied with the internet companies’ plans to crack down on anti-Japanese content. One commenter on NetEase accused the platform of being “an enemy of the Chinese”. The Chinese authorities said the knife attack, which came two weeks after four US educators were stabbed while visiting a park in the north-eastern province of Jilin, was an isolated incident.