Three people were stabbed outside the prestigious University of Tokyo ahead of nationwide college entrance exams Saturday, with police saying they had arrested a high-schooler for allegedly carrying out the attack.

The victims included an 18-year-old boy, a 17-year-old girl and a 72-year-old man, police said.

"We arrested a 17-year-old male student for allegedly slashing in the back (of the three) with the intent to kill," a Tokyo police spokesman told AFP.

The student was seized by police at the gate of the University of Tokyo after the early morning attack, they added.

He was not taking the exams and was not acquainted with the three victims, but told police he "wanted to die after causing an incident as I didn't do well in my studies," public broadcaster NHK reported.

The two teenagers did not sustain life-threatening injuries but the 72-year-old is severely wounded, according to local media.

NHK said the university, where 3,700 students were scheduled to take the tests, went ahead with the exams as planned.

Violent crime is rare but stabbings do occasionally happen in Japan, where gun possession is strictly controlled.

A 24-year-old man was arrested in Tokyo on Halloween last year for attempted murder after he allegedly stabbed a passenger and started a fire inside a moving train while wearing an outfit reminiscent of comic villain the Joker.