TEHRAN (Reuters) - Iran´s Health Ministry said on Saturday the country had no human cases of the deadly H5N1 bird flu virus, dismissing statements by a medical official and lawmaker that early tests showed a third person had died of it.

A senior medical official told Reuters on condition of anonymity that preliminary tests in the northwestern city of Kermanshah showed a 30-year-old man died on Wednesday morning from H5N1 bird flu.

He said this would be the third death after a 41-year-old man and his 26-year-old sister were also shown by preliminary tests to have died of bird flu in Kermanshah, which lies some 100 km (60 miles) from the Iraqi border.

Kermanshah´s parliamentarian Jahanbakhsh Amini was quoted by the Etemad-e Melli newspaper as saying: "Preliminary tests on three members of a family who died in a suspicious manner in Kermanshah were positive."

However, Amini told Reuters these samples were then sent to Tehran where laboratories reported they were negative.

The Health Ministry said no "credible" tests had delivered a positive result on H5N1.

"The Health Ministry denies any news of bird flu cases in Kermanshah," it said in a statement.

Amini said samples would have to be sent abroad for checks by the World Health Organization (WHO) to end the confusion.

The WHO said on Thursday it had asked Iran for details on the tests run on two dead pneumonia patients that the government said were negative for H5N1.

However, Iranian officials said it was untrue that the WHO was seeking more details.

Iran´s neighbors Turkey, Iraq and Azerbaijan have all reported deaths from the H5N1 virus in recent months but Tehran says it has so far found no human cases.

"Although in the initial phases one of the diagnoses was bird flu, we could not spread terror among the people by saying it was 100 percent certain that it was bird flu," Amini said.

The medical official said Roche AG´s Tamiflu bird flu treatment was being given to all staff at the hospital where the three died.

If confirmed in western Iran, human H5N1 would come as a big blow.

Iran´s poultry industry employs 600,000 people directly but the Union of Chicken Meat Farmers says as many as three million people are dependent on the fowl trade. A commercial cull would be devastating.

Iran´s provinces along the Turkish and Iraqi borders are already simmering with social and ethnic discontent from minorities such as the Arabs, Kurds and Azeris.

Iran first reported H5N1 in February, when the virus was found in wild swans.

The H5N1 virus remains mainly a virus of birds, but experts fear it could change into a form easily transmitted from person to person and sweep the world, killing millions within weeks or months.