Schools across China have been ordered to step up security measures after a series of bloody attacks on children and teachers in recent days.

As part of the increased security, armed police were to begin patrolling schools in Beijing after the May Day holiday, officials said.

On Saturday, the state-run Xinhua news agency quoted Hao Ping, China's education vice-minister, as saying that authorities faced a "heavy task" with 270 million students in schools across China.

Hao said the government was setting up a 22-member expert team to focus on "public incidents" in the education system, according to Xinhua.

The crackdown follows an attack on Friday in the city of Weifang in which a farmer broke into a school, attacking children and a teacher with a hammer before setting himself on fire and burning himself to death.

Friday's attack was the third such incident in three days, and the fifth in the space of just over a month.

Pupils wounded

On Wednesday, a 33-year-old former teacher broke into a primary school in the southern city of Leizhou, wounding 15 pupils and a teacher with a knife.

The attacker had reportedly been on sick leave from another school since 2006 for mental health problems.

A day later, a 47-year-old unemployed man armed with a 20-centimetre knife wounded 29 young children, as well as two teachers and a security guard at a school in the eastern city of Taixing.

Five of the injured children were reported to be in a serious condition in hospital.

Parents of children at the Taixing school have been protesting outside a city hospital demanding better security measures in response to the attacks.

The attacks have been given little coverage in Chinese state media, in what observers say may reflect a desire to avoid further copy cat attacks, or to avoid overshadowing blanket coverage of the opening of the showpiece Shanghai Expo, a pet government project.