The bird flu virus detected in Romania is the same lethal strain which struck in Asia.
The authorities have been treating the outbreak with great caution
Confirmation came following tests at the Veterinary Laboratory Agency in Weybridge in the UK.
The H5N1 strain has caused heavy losses of livestock in south-east Asia since 2003 and more than 60 human deaths.
Although its human victims contracted the disease from contact with birds, there are fears a mutant form of the virus may start passing between humans.
The WHO has warned millions could die in a global pandemic if this happens.
Cases of bird flu were reported in two villages in eastern Romania earlier this month.
The test result confirms that the lethal variant of the virus has arrived on the European continent.
H5N1 BIRD FLU VIRUS
Principally an avian disease, first seen in humans in Hong Kong, 1997
Almost all human cases thought to be contracted from birds
Isolated cases of human-to-human transmission in Hong Kong and Vietnam, but none confirmed
"The results are that it is H5N1 but further laboratory results are required in order to confirm the origin of the virus," said a spokesman for the UK agriculture ministry.
Romanian officials have said further drastic measures will be needed to contain the outbreak.
Domestic poultry has already been culled in the affected area, and a 3km quarantine zone has been set up around it.
Romanian agriculture and veterinary officials are to meet local and government politicians to discuss a response to the outbreak.
'No risk to public'
Turkey has already reported the discovery of the lethal strain of the virus among birds in the west of the country.
The EU has banned imports of live birds and poultry products from Romania and Turkey.
Speaking after it was confirmed that the strain of bird flu discovered in Romania was the same as that in Turkey, EU Health Commissioner Markos Kyprianou said action had already been taken.
"The Commission had already been working on the assumption that the virus found in Romania was also the H5N1 strain," he said. "Therefore appropriate measures are already in force."
EU veterinary experts said on Friday that the bird flu outbreak did not represent a risk to the general public "at present".
In a statement released after talks in Brussels they said the disease "remains confined to poultry and wild birds".
They urged governments to identify areas where the disease was most likely to strike and to make sure poultry was not exposed to wild birds.
The H5N1 strain remained largely in South-East Asia until this summer, when Russia and Kazakhstan both reported outbreaks
Scientists fear it may be carried by migrating birds to Europe and Africa but say it is hard to prove a direct link with bird migration