China has culled 80,000 chickens in the country's north after detecting an outbreak of H7N9 bird flu on a farm of layer hens, said the agriculture ministry on Friday.

Five thousand hens on the farm in Xingtai in Hebei province died in late April, said the ministry, and another 8,500 hens were infected with the disease.

After confirming infection with the H7N9 virus, authorities ordered the culling of 80,057 poultry. The outbreak is under control, added the statement.

Infection with bird flu usually peaks during winter months and tails off in the spring but cases of H7N9 have been unusually high in the country since last year.

More than 200 people have died since last October and new cases continue to be reported, with the latest fatality occurring in Shaanxi province this week.

Outbreaks among birds have spread northwards, and the virus has evolved from a low pathogenic one into one with more serious symptoms.