BEIJING -- Seven students were killed Friday in a stabbing rampage at a middle school in China's northwest, authorities said. State broadcaster CCTV said the attack happened in Shaanxi province's Mizhi county as students were leaving the No. 3 Middle School. It said 12 other students were injured.

A suspect identified by the surname Zhao has been arrested, CCTV said. Police said the suspect is 28 years old and a former student of the school, the BBC reports.

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. Police said five girls and two boys were killed in the attack.