Japanese Prime Minister Shinzo Abe called the incident "extremely harrowing," the AP reported.
"I feel strong resentment," he said, adding: "I will take all possible measures to protect the safety of children."
>> See the tweet here
U.S. President Donald Trump, who was in Japan on a state visit, also expressed his condolences.
"I want to take a moment to send our prayers and sympathy to the victims of the stabbing attack this morning in Tokyo," Trump said, according to the AP. "All Americans stand with the people of Japan and grieve for the victims and their families."
Read more here or here.
– The Associated Press contributed to this report.