Image copyright Reuters/CCTV Image caption Chinese TV showed a large crowd gathered outside the nursery

An explosion at the gates of a Chinese kindergarten that killed eight people was caused by a 22-year-old man who died in the blast, police say.

Bomb-making materials were found in the flat where the man, named as Xu, lived, and the words "die" and "death" had been scrawled on the walls.

The blast happened just as parents in Fengxian in the eastern province of Jiangsu were picking up their children at the end of the day.

It is being treated as a criminal act.

Xu had suffered from health problems and had dropped out of school but was employed, police said.

More than 60 people were injured in the explosion, including eight who are in a serious condition, the authorities say.

A survivor told Chinese state TV that the kindergarten gate had just opened for children to leave but none had come out when the blast happened.

Fengxian officials said none of the children or teachers at the kindergarten were among the casualties.

The Fengxian blast is the second tragedy to strike a Chinese kindergarten in recent weeks.

Last month, 11 children died when a bus packed with kindergarten pupils burst into flames inside a tunnel in eastern Shandong province.

It later emerged that the fire had been started deliberately by the driver, who also died.

There have also been knife attacks at schools in recent years. In January a man with a kitchen knife wounded 11 children at a kindergarten in southern China's Guangxi province.

Last February a knifeman stabbed 10 children outside a primary school in the island of Hainan in southern China before killing himself.

Such attacks have generally been attributed to people with personal grudges or suffering from mental health problems.

However Chinese leaders have in the past also acknowledged that underlying social tensions have contributed to the crimes.