HANOI, June 2 (Reuters) - A Vietnamese man who works at a poultry slaughterhouse outside Hanoi has been infected with bird flu, the country"e;s second human case in less than a month, state media on Saturday quoted a doctor as saying.

The man was taken to hospital with fever on May 26 and tests conducted in Vietnam confirmed he had the H5N1 virus, doctor Nguyen Duc Hien who heads the hospital treating the man told the Thanh Nien newspaper.

He told the newspaper the patient was in stable condition.

Hien could not be reached for comment.

Last month Vietnam reported its first human case of H5N1 virus infection in a year and a half, a 30-year-old man in a province neighbouring Hanoi who became sick after helping slaughter chickens at a friend"e;s wedding.

The World Health Organisation (WHO) said it was working with the Vietnamese government to verify that suspected case.

Hien said three more people had been admitted to his hospital in recent weeks with serious pneumonia, and one of them had died.

Doctors had suspected the three had bird flu but tests showed they did not, the doctor told Thanh Nien.

Bird flu has hit chickens and ducks in 13 provinces and in Can Tho city since early May.

A total of 42 Vietnamese have died since the virus re-surfaced in Asia in late 2003. It then re-emerged in 2005, last year and early this year.

The virus has infected 309 people in 12 countries, 187 of whom have died, according to WHO figures. These did not include the death on Tuesday of a 15-year-old Indonesian girl.