The killer virus of H5N1 Avian influenza has been detected in the fourth province of Afghanistan, said a press release issued by the UN Food and Agriculture Organization (FAO) yesterday.

"According to the results of tests, H5N1 Highly Pathogenic Avian Influenza cases have been definitely confirmed in four provinces, namely Kabul, Nangarhar, Logar and Kapisa," said the press release.

Earlier the agency, through tests conducted in FAO's laboratory in Italy, had confirmed the spread of epidemic in three provinces, including the country's capital city Kabul.

Kapisa is the fourth province where the deadly virus of H5N1 has been confirmed while the neighboring provinces of Parwan and Laghman have been classified as "highly suspected."

The FAO has so far conducted tests on 103 samples Afghanistan's birds in its Italy's laboratory since February.

However, no case of transmitting the disease to human has been reported so far.

"Based on the current available data it seems that the disease is slowly spreading. FAO is supporting initiatives to strengthen active surveillance in order to promptly identify ongoing outbreak," the press release noted.