Agriculture Minister Evangelos Basiakos said the H5 virus had been detected in one of nine turkeys tested on Oinouses.
Preliminary tests have identified bird flu and narrowed down the virus to the H5 type, but more rigorous testing is being conducted to determine whether it is the deadly H5N1 strain that scientists are tracking for fear it could mutate and spawn a lethal human flu pandemic capable of killing millions.
According to Basiakos, the owner of a small turkey farm with 20 birds informed the local veterinary service about "the presence of strange symptoms and losses among the turkeys."
A veterinary team from the nearby island of Chios traveled to Oinouses, a five-square-mile island with a population of about 700 people, and took samples from the suspect birds.
Tests carried out in Athens found that one of the nine samples tested positive for the H5 virus. The ministry ordered that new samples be taken and sent to a central veterinary testing center in the northern port of Thessaloniki as "there is a pressing need for verification of the analysis."
The ministry placed the farm under quarantine, banning the movement of all people, vehicles, animals, meat, eggs and carcasses from it without ministry permission. It also ordered an immediate disinfection of the farm.
Health services in Greece and elsewhere in Europe had already been on alert after the deadly H5N1 strain of bird flu was confirmed in Romania and Turkey.
Last week, Greece invited health ministers from Balkan and Black Sea countries to coordinate actions on dealing bird flu — but a date for the meeting has not been set.
Greek veterinary authorities have also increased inspections of migratory birds at six wetland areas around the country, with daily samples to be sent to two state laboratories.
Meanwhile, the European Union, seeking to calm fears on the continent, said Monday that bird flu poses a "minimal" risk to Europe's general public.
The European Center for Disease Prevention and Control will present guidelines Friday on how workers who deal with infected animals can protect themselves against infection, agency chief Zsuzsanna Jakab said.
But she urged calm about bird flu, which is difficult for humans to contract and rarely transmitted between people.
"The risk to human health, to public health, at this stage is minimal," Jakab said from Stockholm, Sweden, the EU agency's new headquarters.
"There is a little more risk for those who have directly worked with the infected animals, so our goal must be to further minimize that risk," she said.
However, Jakab said it was important that countries continue their preparedness for a pandemic of different viruses, not just bird flu.
"Looking at the history of mankind, there have been pandemics on an average every 25 years this century," she said. So "the only thing we know is that there is going to be a pandemic ... but we do not know from which virus" or when it might strike.