Five other people from the same region of eastern Turkey, four of them children, are undergoing tests in Van hospital near the Iranian border after exhibiting flu symptoms and failing to react to antibiotics.
Huseyin Avni Sahin, the head doctor at the hospital, said: "Mehmet Ali Kocyigit, 14, died despite all our efforts to save him."
He said a team of experts from the capital, Ankara, would travel to the region on Monday to investigate the cause of death.
Turkey, which lies on the path of migratory birds that are believed to spread the virus, has suffered two outbreaks of the disease among poultry in the past three months, the latest last week in the eastern province of Igdir.
No humans are known to have contracted the disease in Turkey or Europe, though veterinary authorities across the continent have been culling birds and taking other precautionary measures since outbreaks in Turkey and Romania in October.
In the Igdir outbreak, the strain has been identified as the H5 type but authorities are conducting further tests to see whether it is the deadly H5N1 variant that has killed people in east Asia since 2003 and prompted the slaughter of millions of birds.
"Mehmet Ali Kocyigit, 14, died despite all our efforts to save him"
Huseyin Avni Sahin,
head doctor, Van hospital
Turkey has sent samples from Igdir to the World Health Organisation and the European Union for more tests.
All six of the Van patients, including the dead boy, are from the district of Dogubayazit, a remote, rural area where farming and animal husbandry are the main form of livelihood.
The Anatolia state news agency quoted local officials as saying they had banned all transportation of poultry in Dogubayazit and that culling would begin soon as a precautionary measure.
Zaman newspaper said on Sunday that authorities in Erzurum province - also in eastern Turkey - had culled more than 700 poultry in recent days after 15 chickens died "in suspicious circumstances".
Blood is drawn from patients to
analyse in suspected cases
The outbreak of bird flu in October occurred in northwestern Turkey, triggering the culling of more than 10,000 birds. That outbreak was identified as the H5N1 strain. Several people were briefly kept in hospitals.
The Agriculture Ministry declared that region free of bird flu early last month, but scientists say the country remains vulnerable because of the movements of migratory birds.
The Turkish authorities say they believe that the Igdir outbreak was caused by migratory birds from the Caucasus.