International bird flu experts have gone to the eastern Turkish region of Van, to try to find out how quickly the deadly H5N1 strain is spreading.
Critics say the emergency bird cull has been too slow
Turkish officials reported five new human cases of bird flu on Monday, detected in several provinces.
Earlier, two children and an adult tested positive for H5N1 in Turkey's capital Ankara, the city's governor, Kemal Onal, said.
At least two children died of H5N1 in the eastern village of Dogubeyazit.
A mass cull of poultry is under way in the area.
A Turkish health ministry official said the latest bird flu cases raised to 14 the number of people infected across the country.
Turkish officials stress there is no sign yet the virus has mutated into a much-feared form that could pass between humans.
The Ankara outbreak has not been confirmed by World Health Organization labs, but is still likely to trigger panic, says the BBC's Sarah Rainsford in Turkey.
If confirmed, the cases will be Turkey's first outside the eastern region of Van, about 1,000km (620 miles) away.
Our correspondent says the three people who tested positive in Ankara come from a town about one hour's drive from the city.
Officials have asked locals to bury their own poultry
It is not clear how they could have contracted the disease, although there were reports of ducks in the town having the virus.
The results will now be checked by scientists at the WHO laboratory in London.
In the eastern town of Dogubeyazit, in Van, three children from the same family died last week, at least two of them from the virulent H5N1 bird flu strain which has killed more than 70 people in South-East Asia.
Tests are still under way on the third child to see if she also died from H5N1.
All three children - a 14-year-old boy and his 11 and 15-year-old sisters - were living in close contact with poultry and there is still no evidence that the disease has begun to spread between humans.
Nonetheless a local hospital has been besieged by panicked residents seeking treatment for symptoms.
Twenty people remain in hospital in the city of Van receiving treatment for suspected bird flu.
The WHO has attempted to play down fears of the disease, as Turkish officials sought to defend themselves from accusations they were slow to act. Officials have now asked residents to dig pits and bury their own birds.
Officials say they have had difficulty persuading people in the impoverished rural region to deliver all of their poultry up for slaughter, whether the birds appear healthy or not.
Meanwhile Iran, which shares a border with eastern Turkey, has closed one of its border crossings, officials told Turkey's Anatolia state news agency.
Indonesian authorities confirmed on Monday that a 39-year-old man died of bird flu on 1 January, after he had come into contact with chickens that had died from the deadly strain.
If confirmed by the WHO as a victim of H5N1, the case would be the 12th fatality from the strain in Indonesia.