The experts were seeking to confirm whether cases of bird flu in Romania resulted from the H5N1 variant of the disease, which could provoke a deadly global pandemic among humans.

The European Commission in Brussels said it was banning poultry imports from Turkey after avian influenza was identified there, although not tied to specifically to the H5N1 variety.

Authorities in the northwestern Turkish province of Balikesir slaughtered hundreds of birds overnight after the flu was detected in the region, while the health ministry assured humans they had nothing to fear.

Nearly 3,000 birds were gassed and buried in lime pits in Kiziksa, where the first case of bird flu in the country was confirmed at a turkey farm over the weekend and some 2,000 birds were initially slaughtered, the sub-governor of Manyas district, Resul Celik, said.

Birds in Turkey tested positive for the avian influenza virus "but the exact strain is not yet known, nor is it known if the strain is of high or low avian influenza," the commission said.

Meanwhile, initial tests at a Bucharest laboratory on embryo-containing eggs failed to give a positive reading for the H5N1 variety Sunday, the commission said.

It said it was sending experts along with reagents to carry out a second round of tests on embryonated eggs, and that results were expected by Friday.

Hungary Monday joined Poland in banning poultry imports from Romania in growing economic disruption caused by the outbreak, which could have a devastating impact on agricultural production even if the disease is caused by a strain to which humans are immune.

Austria announced it was building up stocks of face masks, disinfectant and vaccine in case avian flu spreads there. Greece said it was reinforcing preventive measures. Switzerland said it was builidng up a stock of 100,000 doses of vaccine to protect people who might come in contact with the virus.

In the Netherlands, which slaughtered some 25 million head of poultry as a result of an outbreak of bird flu in 2003, Agriculture Minister Cees Veerman said measures would have to be adopted "immediately" if the Romanian samples test positive for avian influenza. "There is a lot of uncertainty," he said. "We need to know what is rumor and what is not."

In Turkey, the flu was detected close to a nature reserve and lake that attracts migratory birds, feared to have brought the disease from Russia and central Asia.

A senior health official in the region, Adnan Pac, said all birds in a three-kilometer (two mile) quarantine zone would be slaughtered and that the quarantine would be maintained for three weeks.

In Romania, nearly 15,000 birds were scheduled to be slaughtered and incinerated around the village of Ceamurlia de Jos.

The potentially killer H5NI strain has infected 112 people in 10 southeast Asian nations, of whom 60 have died. The cases were mostly infected directly by birds, and experts say the disease does not easily spread from person to person.

However, the fear is that the disease could be highly infectious if it mutated with ordinary kinds of influenza that could turn it into a global pandemic.

To reduce the risk of this happening, both Turkey and Romania were giving flu shots to populations at risk.

Romanian officials said up to 125,000 people in the Danube delta, where the first suspected cases have been identified, are due to be vaccinated. In addition, vaccination campaigns were being carried out in six regions.

"It is very important because it leads to a strengthening of general immunity," said a health ministry official, Oana Grigore.

Although the flu strain found in Romania had not been confirmed as being the H5N1 variety, "we have to act as though it were," said Agriculture Minister Gheorghe Flutur.