The blast occurred around 4.50 p.m. at the gate of the kindergarten in Fengxian county as the children were leaving the pre-school.
Two people died at the scene and another five died later in hospital, Xinhua news agency reported.
Among the injured, nine remained in critical condition, the authorities said. It is not known how many children, if any, were among the casualties.
A video of the incident circulating on the social media showed chaotic scenes at the gates, with several children as well as adults lying on the floor, many of them injured and their clothes torn.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)