Romanian authorities called for all farm birds in the southeastern Danube delta to be kept indoors after the country's first three cases of bird flu were detected in the region.
"The virus has been identified in three ducks in the village of Ceanurlia de Jos (southeastern Romania)," Agriculture Minister Gheorghe Flutur said.
"We have already imposed quarantine measures in the village and the health authorities in the Danube delta have been put on alert," he told a press conference.
"The virus was probably carried into Romania by migrating birds from Russia," Flutur said.
The Romanian test results were to be sent to a European Union-approved laboratory in Britain for further analysis.
Health Minister Eugen Nicolaescu said the government would step up its anti-flu vaccination campaign for residents of the Danube delta, a haunt of migrating birds.
Romanian authorities took steps last month to start vaccinating all birds in the delta in a bid to prevent a spread of bird flu.
A strain of bird flu known as H5N1 has killed 63 people in Southeast Asia since 2003, most of them in Vietnam.
The World Health Organisation's biggest fear is that H5N1 may mutate, acquiring genes from the human influenza virus that would make it highly infectious as well as lethal, possibly killing millions worldwide.
No specific vaccine can be produced until the virus mutates, but antiviral medication might be effective if given quickly when symptoms develop.
