Three suspected Islamic State suicide bombers who killed 42 people in a gun and bomb attack at Istanbul airport this week were from Russia, Uzbekistan, and Kyrgyzstan, a Turkish government official said on Thursday.
The official gave no further details beyond confirming the attackers' nationalities and declined to be named because details of the investigation have not yet been released. Investigators had been struggling to identify the bombers from their limited remains, officials said earlier.
"A medical team is working around the clock to conclude the identification process," one of the officials told Reuters.
The three bombers opened fire to create panic outside, before two of them got inside the terminal building and blew themselves up. The third detonated his explosives at the entrance. A further 239 people were wounded in the Tuesday attack on Europe's third-busiest airport, the deadliest in a series of suicide bombings in Turkey this year.
The pro-government Yeni Safak newspaper said the Russian bomber was from Dagestan, which borders Chechnya, where Moscow has led two wars against separatists and religious militants since the Soviet Union collapsed in 1991.
The Kyrgyz security service declined to comment, while the Uzbek security service could not immediately be reached.
Turkish police detained 13 people, three of them foreigners, in raids across Istanbul in connection with Tuesday night's attack.
Counter-terrorism teams led by police special forces launched simultaneous raids at 16 locations in the city, two officials told Reuters. Turkish authorities have said they believe Islamic State was behind the airport attack.
Yeni Safak reported that the organizer of the attack was suspected to be a man called Akhmed Chatayev, of Chechen origin. Chatayev is identified on a United Nations sanctions list as a leader in Islamic State responsible for training Russian-speaking militants, and is wanted by Russian authorities.
The Hurriyet newspaper named one of the attackers as Osman Vadinov, also Chechen, and said he had come from Raqqa, the heart of Islamic State-controlled territory in Syria.
Turkish officials did not confirm to Reuters that either Chatayev or Vadinov were part of the investigation.
Thousands of foreign fighters from scores of countries have crossed Turkey to join Islamic State in Syria and Iraq in recent years. Turkey has tightened security on the Syrian border but has long argued it needs more information from foreign intelligence agencies to intercept the fighters.
Estimates vary on the number of fighters who have joined from Central Asian countries, which include Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. Overall, there may be as many as 4,000 Central Asians who have traveled to the caliphate. Officials in Kyrgyzstan have previously claimed that at least 500 of its citizens are fighting with Islamic State.
Wars in neighboring Syria and Iraq have fostered a home-grown Islamic State network blamed for a series of suicide bombings in Turkey, including two others this year targeting foreign tourists in the heart of Istanbul.
Islamic State has established a self-declared caliphate on swathes of both Syria and Iraq and declared war on all non-Muslims as well as Muslims who do not accept its ultra-hardline vision of Sunni Islam. It has claimed responsibility for similar bomb and gun attacks in Belgium and France in the past year.
Turkey, a member of the NATO military alliance and part of the US-led coalition against Islamic State, has repeatedly fired back on the Sunni hardliners in recent months after rocket fire from northern Syria hit the border town of Kilis.
In a sign of the growing threats to Turkey, US defense sources said on Wednesday that Washington was moving towards permanently banning families from accompanying US military and civilian personnel deployed in the country.
Critics say Turkey woke up too late to the threat from Islamic State, focusing instead in the early part of the Syrian civil war on trying to oust President Bashar al-Assad, arguing there could be no peace without his departure.Once a reluctant partner in the fight against Islamic State, Ankara adjusted its military rules of engagement this month to allow NATO allies to carry out more patrol flights along its border with Syria.
Follow VICE News on Twitter: @vicenews