BEIJING: Two Shanghai men have died from a little-known type of bird flu in the first known human deaths from the strain.

Chinese authorities said Sunday that it wasn't clear how the men were infected, but that there was no evidence of human-to-human transmission.

A third person, a woman in the nearby province of Anhui, also contracted the H7N9 strain of bird flu and was in critical condition, China's National Health and Family Planning Commission said in a report on its website.

There was no sign that any of the three had contracted the disease from each other, and no sign of infection in the 88 people who had closest contact with them, the medical agency said.

H7N9 bird flu is considered a low pathogenic strain that cannot easily be contracted by humans. The overwhelming majority of human deaths from bird flu have been caused by the H5N1 strain.

One of the two men from Shanghai, who was 87, became ill on Feb. 19 and died on Feb 27. The other man, 27, became ill on Feb. 27 and died on March 4, the agency said. A 35-year-old woman in the Anhui city of Chuzhou became ill on March 9 and is being treated.

The Chinese Center for Disease Control and Prevention conducted tests and confirmed Saturday that all three cases were H7N9, the health agency said, adding that the World Health Organisation had been notified of the findings.