Turkish investigators pored over video footage and witness statements on Wednesday after three suspected Islamic State suicide bombers opened fire and blew themselves up in Istanbul's main airport, killing 36 people and wounding almost 150.
The attack on Europe's third-busiest airport was one of the deadliest in a series of suicide bombings in recent months in Turkey, part of the U.S.-led coalition against Islamic State and struggling to contain spillover from neighboring Syria's war.
President Tayyip Erdogan said the attack should serve as a turning point in the global fight against terrorism, which he said had "no regard for faith or values".
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One attacker opened fire in the departures hall with an automatic rifle, sending passengers diving for cover and trying to flee, before all three blew themselves up in or around the arrivals hall a floor below, witnesses and officials said.
Video footage showed one of the attackers inside the terminal building being shot, apparently by a police officer, before falling to the ground as people fled. The attacker then blew himself up around 20 seconds later.
"It's a jigsaw puzzle ... The authorities are going through CCTV footage, witness statements," a Turkish official said.
The Dogan news agency said autopsies on the three bombers, whose torsos were ripped apart, had been completed and that they may have been foreign nationals, without citing its sources.
Broken ceiling panels littered the curb outside the arrivals section of the international terminal. Entire plates of glass had shattered, exposing the inside of the building, and electric cables dangled from the ceiling. Cleanup crews swept up debris and armed police patrolled as flights resumed.
"This attack, targeting innocent people is a vile, planned terrorist act," Prime Minister Binali Yildirim told reporters at the scene in the early hours of Wednesday morning.
"There is initial evidence that each of the three suicide bombers blew themselves up after opening fire," he said. The attackers had come to the airport by taxi and preliminary findings pointed to Islamic State responsibility.
Two U.S. counterterrorism officials familiar with the early stages of investigations said Islamic State was at the top of the list of suspects even though there was no evidence yet.
No group had claimed responsibility more than 12 hours after the attack, which began around 9:50 p.m. (1850 GMT) on Tuesday.
Istanbul's position bridging Europe and Asia has made Ataturk airport, Turkey's largest, a major transit hub for passengers across the world. A Ukrainian and an Iranian were among the dead, officials from the two countries said. Saudi media said seven Saudis were among the wounded.
"There were little babies crying, people shouting, broken glass and blood all over the floor. It was very crowded, there was chaos. It was traumatic," said Diana Eltner, 29, a Swiss psychologist who was traveling from Zurich to Vietnam but had been diverted to Istanbul after she missed a connection.