Poland has confirmed its first case of the deadly H5N1 strain of the bird flu virus, in two wild swans.
Polish authorities have imposed a security cordon around the area
Officials at Poland's national laboratory said they had identified the virus in birds found near a river in the northern city of Torun.
Poland has imposed emergency measures near the site to fight the outbreak.
Authorities in the country had been on the lookout for bird flu after outbreaks of H5N1 were reported across Europe in recent weeks.
Jan Zmudzinski, deputy director of Poland's Pulawy laboratory, said that the virus was "definitely H5N1".
Samples would now be sent to the EU laboratory in Weybridge, UK, for further examination, he said.
"We are following all the procedures in force in the European Union," he said.
In other developments:
- Officials in Serbia say they have detected H5N1 in swans found dead in northern and western parts of the country, although samples have been sent to the UK for confirmation
- Austria says it has detected the potentially lethal strain in several live cats in the southern state of Styria. It follows the discovery of H5N1 in a dead cat in Germany last week
- Experts at a three-day World Health Organisation meeting urge countries to improve plans for preventing the potential spread of a human flu pandemic.
On Sunday, the authorities imposed restrictions around the site on the bank of the River Vistula, where the birds were found. A crisis centre has also been set up.
On a visit to the area at the weekend, Polish Prime Minister Kazimierz Marcinkiewicz said Poland was ready to tackle an outbreak of the virus.
Concerns had risen since Friday when a dead swan with the H5N1 virus was found on the River Oder, the border between Poland and Germany.
Germany confirmed its first cases of the virus in February.
The H5N1 virus can be caught by humans who handle infected birds, but it is not yet known to have passed from one person to another.
However, experts fear the virus could mutate to gain this ability, and in its new form trigger a flu pandemic that could kill millions.