A junior high school student was slashed by a man with a knife early Thursday in Tokyo's Edogawa Ward, police said.

The 15-year-old boy told police he was attacked while walking to school by an unknown assailant who approached him from behind. The attacker slashed the boy's left shoulder while yelling incomprehensibly, police said.

The boy went to school after reporting the case to police. The site of the attack was about 1 km southeast of JR Shinkoiwa Station.

The assailant was reported to be about 175 cm tall, about 30 years old and wearing a red short-sleeved shirt and jeans.