BEIJING -- A knife-wielding man went on a slashing rampage in a kindergarten in eastern China, leaving three children and one teacher dead, area residents said Wednesday.

The unidentified assailant entered the school in a suburb of Zibo in Shandong province around 4 p.m. Tuesday as parents were picking up their children, according to people living nearby contacted by telephone.

About 20 children and staff were injured, two of the children seriously, they said.

China this year has suffered a spate of gory attacks on schools and in public spaces, leaving dozens of people dead and scores wounded.

Authorities have responded with increased security at schools and orders to limit media coverage of the attacks to discourage copycats.

Official news media were silent on the attack Wednesday - a likely sign editors were told to avoid the topic. Zibo government officials either refused to provide information or did not answer their phones.

A woman who works in a restaurant opposite the Boshan District Experimental Kindergarten's Jinfengyuan branch said the attacker was a man aged 27 or 28 who gained entry to the school by posing as a parent.

Police rushed to the kindergarten soon after the attack and officers transported some wounded children to a hospital before ambulances had time to arrive, said the woman, who would give only her surname, Zhang.

"The kindergarten has been sealed off until now. There're still police officers there," Zhang said.

Zhang and other area residents said the teacher died of her injuries Wednesday morning.

The Zibo killings came just two days after a man driving an earth mover in Hebei province to the west went on a rampage, smashing vehicles and buildings and leaving 17 dead.

Other recent mass killings include a May 12 attack on a kindergarten in the northern province of Shaanxi that killed seven children and two adults, and the wounding of 29 children at a kindergarten in Jiangsu province in April.

The seemingly unrelated attacks have prompted calls for more attention to diagnosing serious mental illnesses and ignited fears over the toll stress is taking on the nation's emotional health. (AP)