British poultry farmers have been urged to boost security after a case of bird flu was confirmed in the UK.
The National Farmers Union (NFU) said the virus, thought to have been contracted from wild birds, was found in Scotland last week.
It comes after at least 4,500 chickens died from H5N1 avian influenza - which can spread to humans - at a farm in Shaoyang in the southern province of Hunan, China.
Chinese authorities have culled and disposed of 17,828 chickens following the outbreak.
Among NFU recommended measures to promote biosecurity are cleaning and disinfecting vehicles and equipment that have come into contact with poultry and fencing off flocks to separate them from wild birds.
In a statement, NFU Scotland said: "Urgent message for poultry keepers.
"Low pathogenic Avian Influenza (AI), thought to have been contracted from wild birds, was confirmed in a Scottish free range laying flock at the end of last week.
"Please ensure highest levels of biosecurity at this time."
In December, all 27,000 birds at a commercial poultry farm in Suffolk were culled after a number were found to have the H5 strain of avian flu, identified as "low pathogenic".
Vietnam has also confirmed thousand of birds were culled to stop the spread of the disease.
The authorities have culled the birds, mostly chicken and ducks, at farms in Nghe An, Thanh Hoa and Quang Ninh provinces, said the official, who declined to be named.
Thanh Hoa province, 170 km (105 miles) south of Hanoi, has culled 23,000 birds at 10 household farms after they tested positive to the virus, Thanh Hoa newspaper reported on Monday.
"We are concerned that the virus may spread further, and are trying our best to stop the outbreak," the official said.
Apart from culling the birds, the authorities have also disinfected the farms and put a ban on poultry transport from the infected zones, the official said.
H5N6 virus has also been detected in poultry at a farm outside Hanoi, prompting the culling of more than 2,300 birds there, Kinh Te Do Thi newspaper reported.
Vietnam has a poultry herd of 460 million, and small-sized bird flu outbreaks have not been uncommon in the country during the past five years, the official said.
According to the World Health Organisation, human cases of H5N1 occur occasionally, but the virus does not infect humans easily.
However, it is difficult to transmit the infection from person to person.
When people do become infected, the mortality rate is about 60 per cent, said WHO.
People cam become infected by having close contact with infected live or dead birds, or H5N1-contaminated environments.
WHO said: "There is no evidence that the disease can be spread to people through properly prepared and thoroughly cooked food.
"It is safe to eat properly prepared and cooked poultry and game birds. The virus is sensitive to heat.
"Normal temperatures used for cooking (so that food reaches 70C in all parts) will kill the virus."
Shaoyang is about 350 miles from the central city of Wuhan, where the coronavirus outbreak that has so far killed more than 900 people and spread to Britain began late last month.
