The World Health Organization (WHO) on Friday expressed concern over the detection of avian flu among a flock of free-range chickens in Malaysia despite the country's aggressive measures to prevent the entry of the virus. Shigeru Omi, director of the Manila-based WHO Western Pacific Office, said Malaysian authorities on Thursday officially informed his office about the detection of the virus in a village in the northern state of Kelantan, close to the border with Thailand. "It is going to be a long and difficult struggle to eliminate this virus from the environment," he said. "And the longer it takes, the greater the risk to public health." Omi, however, cited the efforts of the Malaysian authorities to prevent the spread of the virus by culling all chickens within a one-kilometer radius of the affected village. Kuala Lumpur has also launched clinical surveillance of poultry within 10 kilometers and banned the movement of poultry within 10 kilometers. Health officials have advised residents in the area to seek prompt medical assistance if they show symptoms of influenza, while hospitals and laboratories throughout the country have been placed on alert. Omi hailed the prompt response and the transparency of Malaysia in dealing with the outbreak, and said WHO would fully support efforts of the government to address the problem. "Transparency such as Malaysia has displayed is vital in the fight against the virus," he said. Omi also endorsed the decision of Singapore to halt the import of poultry and poultry products from Malaysia. Earlier in the year, at least 18 people were killed by an outbreak of bird flu in the region. The spread prompted governments in 10 Asian countries to cull millions of chicken and other fowls, including imported pet birds.