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

A suspect is in police custody.

Chinese police have given his surname as Zhao and say he is a 28-year-old former student of the school.

Their preliminary assessment is that he was motivated to take revenge because he was bullied in his third year (where students are typically aged 13-14), the BBC's Stephen McDonell reports.

• Alarm bells ring over China school attacks

Police say the dead are five girls and two boys.

Photos on social media show several young students lying on the ground, surrounded by shocked onlookers.

The attack happened at the school at around 18:10 local time (10:10 GMT), a local government statement says.

The injured children are receiving treatment in hospital.

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

Knife attacks have made the headlines in China in recent years:

• A spate of unconnected stabbings at schools between 2010 and 2012 left at least 25 dead and more than 100 injured

• 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

• 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

• In February, a knifeman killed a woman and injured 12 others at a Beijing shopping centre?