China has reported two new cases of human bird flu infection, bringing the total this week to three, stoking fears about the spread of the deadly virus at a time when other Asian nations are battling to control outbreaks of the disease.

A man diagnosed with the H7N9 strain of bird flu in Jiangsu province is being treated in Shanghai, the Shanghai Municipal Commission of Health and Family Planning said on its website on Wednesday.

In Xiamen, a city in East China's Fujian province, local authorities ordered a halt to poultry sales in Siming district from Thursday after a 44-year-old man was diagnosed with the H7N9 strain of bird flu on Sunday, Xinhua News Agency reported on Wednesday. The patient is being treated in hospital and is in stable condition, according to the Xiamen Center for Disease Control and Prevention.

The incidents come after Hong Kong confirmed an elderly man was diagnosed with the disease earlier this week.

Bird flu is most common in winter and spring, and farmers have in recent years improved cleaning regimes and animal detention techniques, while building roofs over hen pens and taking other steps to prevent the disease.

However, concerns remain about the spread of the disease as farmers in China are preparing for the year's peak demand during the Lunar New Year at the end of January.

In light of recent outbreaks in nearby countries, farmers in China are feeding their flocks more vitamins, while ramping up vaccines and hen house sterilizations to protect their birds.

Authorities said they would ban imports of poultry from countries where there are outbreaks of highly pathogenic bird flu.

China already prohibits imports from more than 60 nations, including Japan and South Korea.

The last major bird flu outbreak on the Chinese mainland, in 2013, killed 36 people and cost the agriculture sector about $6.5 billion in losses.

He Xiong, deputy director of Beijing Center for Diseases Prevention and Control, said there is no likelihood that the recently confirmed cases would evolve into a major bird flu outbreak in China, as the virus is not transmitted between people, adding that health authorities are well prepared for the control and prevention of the disease.

"People should avoid contact with live poultry to avoid being infected," he said.

"Information exchanges between different provinces and municipalities on new cases is important for the control and prevention of the virus."

Wang Xiaodong contributed to this story.