The man worked as a security guard in Wuhan, the capital of Hubei province, said Aphaluck Bhatiasevi, a spokeswoman for the WHO's Beijing office.

He became sick on April 1 and was suffering from a high fever, she said. He was diagnosed with pneumonia of unknown causes, she said.

"The likely source of exposure is still under investigation and people who had close contact with him are under medical observation," Bhatiasevi said.

The patient has been confirmed to be infected with bird flu in accordance with the standards of the World Health Organization (WHO) and the Chinese official standards, the ministry said.

The man is China's 17th confirmed human case of bird flu since November on the mainland, where 11 people have died from the disease.

The ministry has reported the new case to the WHO and the regions of Hong Kong, Macao and Taiwan, as well as several other countries.

The H5N1 virus has killed 109 people in nine countries, mostly in Asia, according to WHO, and has killed or prompted authorities to destroy 200 million birds.