TOKYO - A Japanese boy stabbed on his way to school in China died early on Thursday, Tokyo's foreign minister Yoko Kamikawa said, an incident that has inflamed tensions between the neighbouring countries.
"I can't help but feel deep sorrow, having been informed that the child passed away before dawn on September 19," she told reporters, slamming the act as "despicable".
Police in Shenzhen said a man had attacked a minor on Wednesday morning and the child was rushed to hospital. The suspect, a 44-year-old man, was seized, they said.
Japanese media reported that the boy was a 10-year-old Japanese national living in the southern Chinese city.
Late Wednesday, before the boy died, Japan's Vice Foreign Minister Masataka Okano summoned Chinese Ambassador to Japan Wu Jianghao to convey "serious concerns" over the attack.
Okano "strongly urged that security be strengthened, including around Japanese schools throughout China", Japan's foreign ministry said.
In June, a Japanese mother and child were injured in another knife attack in Suzhou near Shanghai, which China's foreign ministry described at the time as an "isolated incident".
A 55-year-old Chinese woman died attempting to stop the assailant and was honoured for her actions by the local government after her death.
Kamikawa on Thursday said Japan's consulate in Guangzhou near Shenzhen had also demanded China explain what happened in the latest incident.
"I take this case extremely seriously," she said.
"We will demand again that the Chinese side ensures the safety of Japanese people, and I have instructed my officials to study what kind of additional measures could be taken to prevent a repeat."
The minister did not comment on the possibility that the attacker intentionally targeted a Japanese national.
Wednesday was the anniversary of the "Mukden incident" or "Manchurian incident" on September 18, 1931 -- the seizure of a city in northeast China by Japanese troops, which was followed by the invasion of the wider region.
In the event in the lead-up to World War II, an explosion on a railway was used by Japanese soldiers as a pretext to occupy the city of Mukden, now called Shenyang.
China's foreign ministry also did not comment when asked at a regular briefing about the significance of the date, which state media said was marked on Wednesday with air raid sirens in multiple cities.
Tensions between Tokyo and Beijing have worsened in recent years as China takes a more assertive stance in the region, including in territorial disputes, and as Japan develops security ties with the United States and its allies.