The blast left victims bleeding and weeping, with images posted on state media showing some had their clothes torn off by the force of the explosion, while one woman clutched a screaming child.
The Fengxian county government in eastern Jiangsu province said Thursday's incident was being treated as a "criminal" act, while witnesses told local media the blast may have been caused by a food stall's gas cylinder.
A survivor told broadcaster CCTV from her hospital bed that the school's gate had just opened for kids to leave, though none had come out when the fireball erupted.
The woman, who was holding a baby during the interview as she sat on her bed, said she blacked out and only woke up while being treated.
The Fengxian county government said class had not yet been dismissed and that no teachers or students were among the casualties.
At least eight people were killed and 65 injured, including eight seriously, according to authorities. Two died at the site of the explosion and six while being treated.
Pictures of the scene showed more than a dozen people outside a building, many lying on the ground and some appearing to be unconscious, including a small child.
A video posted by the People's Daily showed emergency workers arriving at the scene with gurneys. Another showed people lying in a hospital.
Online media reports cited a business owner near the kindergarten as saying that around 5:00 pm (0900 GMT) he heard a "bang", and found that there had been an explosion at the kindergarten entrance only 100 metres (330 feet) away.
The Global Times and China Youth Daily newspapers cited witnesses as saying that a gas cylinder at a food stall had exploded outside the kindergarten on the outskirts of Xuzhou city.
Some people on China's Twitter-like Weibo website said the use of gas canisters by roadside food stalls posed a danger.
"How can the city management officers allow a vendor to set up a stall at a school entrance with a gas fuel canister?"
A police car blocked access to the kindergarten early Friday, far from the scene of the tragedy as reporters tried to reach the school.
Public Security Minister Guo Shengkun "demanded enhanced checks of possible risks at densely populated venues" and his deputy was dispatched to the area to conduct the probe, Xinhua news agency reported.
History of attacks
It is the latest tragedy to strike a kindergarten in China in recent weeks.
A school bus packed with kindergarten pupils erupted in flames inside a tunnel in eastern Shandong province on May 9, killing 11 children, a teacher and the driver.
Officials later said the fire was intentionally set by the driver, who was angry at losing overtime wages.
There have also been knife attacks at schools in recent years.
In January a man armed with a kitchen knife wounded 11 children at a kindergarten in southern China.
In February last year, a knife-wielding assailant wounded 10 children in a schoolyard in the southern island province of Hainan, before committing suicide.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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