Turkish sources claim that the three men who carried out the deadly attack on Istanbul’s Ataturk airport on June 28 were all from parts of the former USSR.
One is said to be from Russia’s North Caucasus region and the others from Kyrgyzstan and Uzbekistan.
Turkey believes ISIS was behind the suicide gun and bomb attack that left 44 people dead and some 240 injured.
Meanwhile, Turkish police detained at least 13 suspects in Istanbul and more in Izmir on June 30.
An unnamed Turkish official confirmed for Reuters news agency the dead attackers’ countries of origin after Turkish media reports.
Some agencies named one of the men as Osman Vadinov, said to have crossed into Turkey from the ISIS stronghold of Raqqa in Syria in 2015.
Reports that Osman Vadinov was a Chechen have been denied by an unnamed police source in the North Caucasus, Russia’s Interfax news agency reports.
The organizer of the attack has been named by Turkish media as Akhmed Chatayev, a Chechen believed to have acted as an ISIS recruiter, who is on a US counter-terror sanctions list. His fate was not immediately clear.
ISIS has long recruited members from mainly Muslim parts of the former USSR, with Russian President Vladimir Putin putting the overall number at between 5,000 and 7,000 in October.
However, data published by the Soufan Group security consultants in December suggests the numbers are lower: 2,400 from Russia and 500 apiece from Uzbekistan and Kyrgyzstan.
Turkey’s government has made no official statement on nationalities yet and no-one has said they carried out the attack on June 28.
PM Binali Yildirim said on June 29 that “our thoughts on those responsible for the attack lean towards Islamic State”.