Crowds gathered outside the school after the attack
Twenty-eight children and three adults have been injured by a man with a knife at a nursery school in eastern China, the third such attack in a month.
Officials said five children were taken to hospital in a critical condition after the incident in Jiangsu province.
It follows a knife attack on Wednesday in the south of the country, in which 16 pupils and one teacher were injured.
Earlier that day, a doctor convicted of stabbing eight children to death in Fujian province in March was executed.
The alleged assailant in Jiangsu was named by police as Xu Yuyuan, a 47-year-old unemployed local man.
Reports say he attacked the children at the Zhongzin pre-school in Taixing city as lessons began in the morning, stabbing a security guard who tried to stop him.
By Chris Hogg, BBC News, Shanghai
The spate of attacks in schools is unsettling for the Chinese. Earlier this month the education ministry urged educational institutions to upgrade their security - teaching children safety awareness and hiring security guards.
But this school had a guard who, according to reports, was injured trying to protect the children. And there is little you can teach a class of four-year-olds that will help them when an armed man bursts into their classroom.
Some here are calling for more severe punishments for those who commit this kind of crime. Others suggest that not enough attention's paid to what they call "the voices of the weak". When that happens they say "they take revenge on society".
Police said Mr Xu, who was detained shortly afterwards, was carrying a 20cm (8in) knife, the state-run Xinhua news agency reported.
"The gate-keeper, teachers, and students were attacked. The injured are receiving treatment in hospital. We don't have any reports of deaths yet," an official with the Taixing city government told AFP news agency.
An official named Zhu told AFP the critically-injured children were now in a stable condition.
Most of the injured children were reported to be four-year-olds from the same class.
"The injured have been sent here one after another," an unnamed official at the Taixing No 1 People's hospital told the Associated Press news agency.
"The doctors are now trying their best to save them."
China has witnessed several school attacks in recent years, most blamed on people with personal grudges or suffering from mental illness.
CHINA SCHOOL ATTACKS
29 April 2010 - three adults and 28 children injured in Taixing, Jiangsu
28 April 2010- at least 15 children and one teacher injured in Leizhou, Guangdong
24 March 2010- eight children killed in Nanping, Fujian
November 2004 - eight boys stabbed to death in a school dormitory in Ruzhou, Henan
September 2004 - 28 children knifed in nursery in Suzhou and 24 children at a school in Shandong
August 2004 - pre-school doorman kills one child and injures 14 in Beijing
On Wednesday, at least 15 students and one teacher were injured in a knife attack at a primary school in southern Guangdong province.
Chen Kangbing, 30, was a teacher at the school in Leizhou city but had been on sick leave since 2006, state media reported.
He attempted to throw himself from the roof of the school before he was arrested, said the city's public security chief, Qin Zhucai.
The same day, 42-year-old Zheng Minsheng was executed in eastern Fujian province for stabbing to death eight children in Nanping.
Police said Zheng, who admitted to "intentionally killing" the children, had been upset about a failed relationship. He had appealed against the death sentence.
The BBC's Chris Hogg in Shanghai says the attacks are unsettling in a country where such violent attacks are rare.
Since a spate of attacks in 2004, many schools in China have employed professional guards but the latest incidents have led to public calls for increased security in schools.
China Daily says the education ministry ordered all schools to upgrade their security facilities earlier this month and employ guards.
Schools were also ordered to teach students about safety and ensure young children were escorted home, said the report.
But such measures are expensive, says our correspondent, and in reality there is little that can be done to prevent such acts of violence.
The incidents have also sparked a debate about the motives of the killers, with some suggesting that rapid social change and growing unemployment has led to an increase in psychiatric illnesses.