The Turkish victims are the first human cases reported outside east Asia since H5N1 avian influenza re-emerged in 2003.
Two more people in China are now known to have died from bird flu last month, bringing the death toll there to five.
Indonesian authorities said a 29-year-old woman in Jakarta had been diagnosed as suffering from the virus after contact with dead chickens.
"There is a necessity for a global answer to this crisis," World Health Organisation (WHO) European Regional Director Marc Danzon said in Ankara.
Scientists fear H5N1, which is known to have killed 78 people, could mutate into a form that can spread easily between humans, leading to a pandemic.
Nations across the world are on
alert to combat bird flu
European authorities are stepping up precautions and Turkish health officials will travel to Luxembourg to meet European Commission officials on Thursday.
WHO doctors said on Wednesday there was no sign of human-to-human transmission in the Turkish outbreak. They also said there was no reason for people not to visit Turkey.
However, experts from another UN body, the Food and Agriculture Organisation (FAO), said the virus risked becoming a constant problem in Turkey as it is in poultry in parts of Asia.
"The highly pathogenic avian influenza virus H5N1 could become endemic in Turkey," the FAO said in a statement.
Juan Lubroth, senior FAO animal health officer, said the virus may be spreading despite the measures taken to combat it and urged neighbouring countries to be on high alert.
The world animal healthy body OIE said Ankara should consider poultry vaccination in addition to culling birds.
Two teenagers died last week from bird flu in eastern Turkey. Their dead sister is also a suspected victim.
"The highly pathogenic avian influenza virus H5N1 could become endemic in Turkey"
Food and Agriculture Organisation (FAO)
The virus has rapidly infected birds in some 30 out of 81 provinces. Authorities have stepped up the culling of poultry, with over 300,000 birds killed.
The WHO said that human victims have contracted the disease from close contact with infected poultry, in most cases children playing with birds or helping families kill them for food or sale.
Authorities believe many poor families in the east brought their sick birds into houses when winter hit, increasing the chances of humans catching the deadly virus.
More than 70 people are suspected of having bird flu and are being tested, although a majority of them are not thought to have H5N1. None of the positive cases are life-threatening.
In eastern city of Van, where some 40 people are being treated for suspected bird flu, locals complained that officials had failed to take away chickens running freely in the roads where children play.
"I'm worried for our children. I have been calling people for three days asking them to take the chickens away," Cengiz Isik, a 34-year-old waiter, told Reuters.