A 6-year-old boy was seriously wounded Thursday morning when he was attacked by a man wielding an ax on the premises of a Seoul school for Japanese children, the Japanese Embassy and other sources said.

The 36-year-old assailant, whose name was not available, was immediately seized by a guard and handed over to police, who arrested him on the spot, according to the school. South Korea's Yonhap News Agency reported investigators were treating the incident as attempted murder.

The assailant told police he carried out the attack because he was assaulted by a man who spoke Japanese at a restaurant the previous night, embassy officials said. However, he kept changing his explanation, and his specific motives remain unclear, they said.

The victim, Hiromu Takishima, is the son of Kazunori Takishima, one of the teachers at the school. He was struck twice on the head with the ax, school officials said.

According to the hospital where he was taken, the boy was seriously injured and was undergoing surgery for a fractured skull. School officials later said his injuries were expected to take a month to heal. Thursday was the kindergartener's birthday.

The school was closed for the remainder of the day and all students were sent home.

The assailant entered the school along with parents dropping their kids off and attacked Takishima at around 10 a.m., shortly after the child got off a school bus, Japanese officials said.

The man also attacked Asaka Nakagawa, 6, but she was not injured, school officials said. He also tried to attack other children.

The incident sparked a panic, a school official said. Some 370 children are enrolled at the school, which consists of a kindergarten, elementary school and junior high school.

There are some 6,000 Japanese nationals residing in Seoul, according to Japanese officials.