A post on Sina Weibo shows a screenshot of the live broadcast of the Japan-Tunisia match at World Cup, in which a "rising sun" flag symbolizing Japanese militarism is displayed in the stadium in Monterrey, Mexico.

Japanese fans holding a "rising sun" flag, a symbol of Japanese militarism during World War II, during Japan's match with Tunisia at FIFA World Cup has sparked widespread criticism from Chinese and South Korean fans.

Japan defeated Tunisia 4-0 at Monterrey Stadium in Mexico to strengthen its position in Group F on Saturday, but discussions surrounding the militarist symbolic "rising sun" flag on the stand soon overshadowed the game's result on social media.

Images and videos of the flag quickly circulated on social media. 

The "rising sun" flag is a symbol of Japan's wartime aggression and colonial rule, as it was used by the Imperial Japanese Army before and during World War II when they invaded countries in Asia Pacific including China, South Korea and the Philippines.

Many Chinese netizens condemned the display of the militarist symbol at the international sporting event.

"Stadium litter is easy to sweep away, but spiritual litter is far harder to clear," read one comment that received significant engagement on Chinese social media Sina Weibo, comparing some Japanese fans' post-match cleanup with the appearance of the militarist flag.

Many South Korean fans expressed similar concerns online, accusing the Japanese fans of glorifying Japan's imperial past. Some South Korean media and commentators renewed calls for international sports organizations to take a stricter stance toward the symbol.

South Korean media Chosun Daily published in a commentary on Sunday saying that "Japan's rising sun flag cheering, which reminds both Korea and Japan of their painful history, is absolutely unforgivable." 

For years, South Korean civic groups and politicians have urged international sporting bodies to ban the "rising sun" flag from major competitions, arguing that it carries historical connotations comparable to other wartime symbols.

The controversy has also drawn attention to FIFA's fan conduct regulations.

According to the World Cup tournament guidelines, political, offensive or discriminatory flags, banners and materials are prohibited inside World Cup stadiums. However, FIFA has not publicly commented on the incident involving the Japanese fans.

The issue involving Japan's militarist "rising sun" flag is not without precedent.

In 2017, the Asian Football Confederation fined Japanese club Kawasaki Frontale after its fans displayed the "rising sun" flag during an Asian Champions League match. Kawasaki Frontale was fined $15,000 and ordered to host one future match in AFC club competitions without spectators.

Reports during the 2022 World Cup indicated that FIFA officials and stadium security intervened to prevent some Japanese supporters from displaying the notorious flag inside the stadiums in Qatar.