Several countries have placed import restrictions on German poultry following outbreaks of bird flu in the country, German authorities said on Wednesday.

Japan, South Korea, Hong Kong, Bosnia and Herzegovina and South Africa have put import restrictions on German poultry and poultry products, the German state government of Mecklenburg-Vorpommern said in a statement.

Eight European countries and Israel have found cases of the highly contagious H5N8 strain of bird flu in the past few weeks and some have ordered that poultry flocks be kept indoors to avoid the disease spreading.

Most outbreaks have involved wild birds, but Germany, Hungary and Austria have also reported cases in domestic duck and turkey farms where all poultry had to be culled.

More outbreaks in Europe are likely in the next few weeks as wild birds believed to transmit the virus migrate south, the deputy head of the world animal health body said on Tuesday.

"An impact from the current bird flu incidents in Germany and other parts of Europe were to be expected," Mecklenburg-Vorpommern state agriculture minister Till Backhaus said in a statement.

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The restrictions underline the need for farmers to rigidly apply rules to restrict the spread of animal illnesses, he said.

Bird flu cannot be transmitted through food, but trade restrictions can have a major impact on countries where the disease is present.

The upcoming Christmas season is a critical time of sales for poultry farmers throughout Europe.