Two young children being treated for bird flu in eastern Turkey have been found to have the virulent H5N1 virus.
The cull of poultry is not yet finished in Dogubeyazit
The children are aged five and eight, a World Health Organisation (WHO) spokesman said.
This week three children from the eastern Turkish town of Dogubeyazit died, of whom at least two were found to have the virulent H5N1 strain.
Worried residents have besieged a poorly-equipped local hospital there seeking treatment for symptoms.
The children are being treated in the intensive care department of the hospital in the eastern city of Van.
Some 30 other patients also showing bird flu-like symptoms, mainly children, are also being treated at the hospital.
A delegation of eight WHO experts and the country's Health Minister, Mehdi Eker, flew to the eastern city of Erzurum on Sunday and are expected to make their way to the city of Van by road.
Their arrival has been delayed by bad weather.
They will assess whether or not the outbreak of cases in the region represents the first cases of human to human transmission.
A WHO spokeswoman said the spread of the disease from east Asia was "a concern" but added that the global risk assessment of a human pandemic was unchanged.
"Right now these new cases in Turkey - they don't elevate the global risk assessment, so we're still in the same pandemic alert phase that we've been in for the last couple of years," Maria Cheng told AP news agency.
"But it's something that needs to be monitored very closely."
Turkish authorities believe all three children who died of bird flu in Dogubeyazit, came into direct contact with infected poultry.
Turkish officials are said to be struggling to finish an emergency cull of poultry to contain the virus, with 12,000 birds, chickens and turkeys killed.
The BBC's Sarah Rainsford, in Dogubeyazit, says there is a mixture of fear and anger there, with many residents collecting poultry for slaughter themselves without protective clothing.
Mehmet Ali Kocyigit, 14, and his two sisters Fatma, 15, and Hulya, 11, all died this week.
Tests carried out in a UK laboratory confirmed that Mehmet Ali and Fatma died from the H5N1 strain, which has killed more than 70 in South-East Asia and China.
The children's family kept poultry at their home in Dogubeyazit.
All four children developed symptoms including a high fever, coughing and bleeding in the throat.
Doctors said they had been playing with the heads of chickens who had died of bird flu.
Mr Eker says at least four new outbreaks of bird flu in poultry have been confirmed in the eastern provinces of Igdir and Erzurum and the south-eastern province of Sanliurfa.