Japanese athletes at this month's Youth Olympics in Nanjing have been warned not to wear their official tracksuits around the city due to safety fears.
Delegation chief Yosuke Fujiwara has told Japan's 78 athletes to wear regular clothes outside the Games' venues during the two-week event starting on Saturday to avoid any attack, with relations between Beijing and Tokyo at their lowest level in years.
The teenage athletes will also be encouraged to don face masks to protect themselves from China's notorious air pollution.
"When they are outside we want them to be aware that it might not be totally safe," Fujiwara told the Kyodo news agency.
"In the athletes' village we want them to wear the official Japan tracksuit, but in the city normal clothes are fine."
In an apparent attempt to avoid upsetting the hosts before the second edition of the Youth Games, Fujiwara added: "You can get random attacks on the street in Japan too."
Anti-Japanese resentment runs particularly high in Nanjing, where China says 300,000 people were killed in 1937 as Japanese troops rampaged through the city during their invasion of the mainland. What became known as the Nanking Massacre was the Japanese military's worst atrocity and remains a bitter stain on the two countries' relationship.
Fujiwara's comments came at a time of heightened political tension between Japan and China, which are at odds over claims to islands in the East China Sea and historical grievances tied to Japan's wartime aggression.
Japanese Prime Minister Shinzo Abe's recent decision to relax strict rules governing the country's military has further antagonised Beijing, prompting Fujiwara to issue the warning.
But he insisted that the contestants would still be free to explore the city.
"We think it's better for the athletes to feel the atmosphere in the city from their own perspective," Fujiwara said.
Japanese sports teams and the country's national anthem have been frequently booed in China, most notably at the 2004 Asian Cup football final between China and Japan in Beijing, which ended in a riot after Japan's controversial win.
The Youth Games - open to athletes aged between 14 and 18 - were first held in Singapore four years ago.