Angst-ridden Chinese social media users -- and state outlets -- raised questions over the plight of the country's children Wednesday after several officials were sacked over five runaway boys' deaths.

The five cousins and brothers, ranging from nine to 13 years old, died of carbon monoxide poisoning when they burned coal to try to keep warm as they sheltered from the cold in a bin in the city of Bijie, in Guizhou province.

They were among the vast numbers of children of migrant workers who are left with relatives while their parents earn a living elsewhere.

"The ignorance and apathy in this country leave me speechless and, once again, heartbroken," said one user of China's popular Twitter-like service Weibo.

Two of the three fathers of the boys worked in other parts of China, while the one who laboured in their hometown as a farmer said he and his wife had little time for their boy, Xinhua news agency reported.

The others were put under the care of an elderly grandmother with poor eyesight "who had difficulties even caring for herself". Four of the boys had dropped out of school and the other missed classes regularly, Xinhua added.

"We need to put the 'left behind' children at the top of our agenda," it quoted Hu Jihong, the deputy mayor of Bijie, as saying. "Many uncared-for youngsters are wandering about the streets."

China's one-child policy has fostered a culture of families doting on their only offspring since it was imposed three decades ago, but incidents of abuse or neglect have sparked debate about how children are treated in general.

In recent weeks a kindergarten teacher stirred outrage after an online video showed her lifting a child off the ground by his ears as he cried out in pain.

In October last year a surveillance camera showed passers-by ignoring a two-year-old girl bleeding on the ground after she was struck by two vehicles. The infant died soon afterward.

Four education and civil affairs officials and two school principals in Bijie have been fired over the latest incident, and two district officials suspended.

A local charity manager, Tian Jie, told the Global Times newspaper on Wednesday that broader measures were necessary to prevent future repetitions.

"Firing officials is not enough," Tian said. "More efforts are needed from government and NGOs to make school attractive to children and warn them of the dangers of the outside world."

Another Weibo user blamed the families, saying: "Why didn't they first go after the parents?

"Five children run away for three weeks and regularly disappear for days at a time, and all the while these parents are just sitting at home."