BEIJING — Chinese authorities say seven middle school students have been killed in a stabbing rampage in the country's northwest.

State broadcaster CCTV said the attack happened Friday evening in Shaanxi province's Mizhi county as students were leaving the No. 3 Middle School. It said 12 other students were injured.

CCTV said a suspect identified by the surname Zhao has been arrested.

China tightly restricts private gun ownership, making knives and homemade explosives the most common weapons employed in violent crimes.

No information was given as to a motive, although reports on Chinese social media said the suspect had once been a pupil at the school.