State media reported the Ministry of Public Security has sent a team lead by a vice-minister to the scene.

The Xuzhou city government, which administers the county, said in a statement that two people died at the scene and the five others at hospital. Nine people were in serious condition as of 7.45pm, it said.

The Xuzhou government said it was still investigating the cause of the blast, which occurred

just outside the campus and came as parents were picking up children from school.

Pictures and videos posted online showed at least a dozen people lying outside the gate of the kindergarten. Some victims were seen covered in blood while other appeared to be unconscious and some with their clothes burned off.

Young children could be seen among the injured.

“About 5pm, we heard a blast and thought it might have been a gas explosion at a nearby food vendor,” a local shop owner was quoted as saying by online news portal Sohu. “Many people could be dead,” the witness said.

In one video clip posted online, a man covered in blood can be seen trying to stand up only to collapse again. His clothes appeared to have been burned off.

In a separate video clip, people were heard shouting: “Blast, blast, dial 110 quickly!”

The gate of the kindergarten appeared to have been horribly bent by the blast, with shattered glass littering the scene.