A state-backed Chinese newspaper Sunday blamed "intense" farming methods for heightening the risk of deadly diseases such as H7N9 bird flu crossing from animals to humans.

China has confirmed 18 cases -- including six deaths -- of the new strain of avian influenza, so far confined to its developed east coast, since announcing a week ago that the virus had been discovered in humans for the first time.

"Normally, diseases are likely to break out in poor areas. Why is it the other way around in China?" the Global Times editorial said.

"In China's southern and eastern coastal areas, agriculture, especially animal husbandry, has become more intense and populations more dense," said the English-language edition of the paper, known for its pro-China stance.

"There is greater chance of contact between humans and animals and subsequent diseases. Local authorities have to develop disease prevention and control methods to match this situation, but this is a weak spot in the country's overall development."

Shanghai, which reported two new cases on Saturday to bring the city's total to eight, with four deaths, has banned live poultry trading and shut markets in an effort to prevent spread of the disease.

Nanjing on Saturday followed Shanghai by shutting markets selling live poultry to its more than eight million residents, while Hangzhou culled birds after discovering infected quail.

Chinese authorities maintain there is no evidence of human-to-human transmission for the H7N9 cases, a conclusion echoed by the World Health Organization (WHO).

The Global Times called for higher standards in the agricultural industry and more balanced development, instead of a narrow focus on rapid economic growth.

"China has focused on growth in the past few decades.... But providing balanced development is far more difficult than the pursuit of single-minded growth," the editorial said.

"Higher standards in animal farming, food processing and consumption should be established and enforced," it said.

In March, Shanghai was hit by an embarrassing pollution case which saw more than 16,000 dead pigs floating down the city's main river, discarded by farmers further upstream.

China has been hit be a series of food scandals in recent years, some caused by producers deliberately using sub-standard or illegal ingredients.