At least seven students have been stabbed to death and 12 injured in a knife attack outside a school in northern China, officials say.

The knife-wielding man attacked the students near a secondary school in Mizhi County in Shaanxi province as they were heading home for the day, officials said.

A suspect is in police custody.

Photos on social media showed several young students lying on the floor, surrounded by shocked onlookers, writes BBC.

A local government statement said the attack happened at Mizhi County Number Three secondary school, at around 18:10 local time (10:10 GMT).

The injured children are receiving treatment, the propaganda department of Mizhi County in Shaanxi province said on social media.

Their exact ages have not been given, but reports suggest they may be middle school children, which would make them aged 12 to 15.

Police have not commented on the attacker's possible motive.

China has seen several fatal knife attacks in recent years. The fact the latest stabbing targeted schoolchildren recalls a spate of unconnected knife attacks at Chinese schools between 2010 and 2012, which left at least 25 dead and more than 100 injured.

More recently, a knifeman killed a woman and injured 12 others at a Beijing shopping centre in February.

In July 2017, two people died and nine were injured by a knife-wielding man at a Wal-Mart supermarket in the southern city of Shenzhen.

The country executed three men in March 2015 after they were found guilty of a savage knife attack at Kunming station, where 29 people were hacked to death and more than 100 others wounded. The trio had been convicted of murder and terrorism offences.