A brazen assault by three suicide bombers on Istanbul's Ataturk Airport has set the stage for a more violent conflict between Turkey and Isis (Islamic State), a development that would deepen Turkish involvement in the Syrian war.
There has been no claim of responsibility for Wednesday's carnage, but Turkish officials blamed the Sunni extremists for the attack, which killed 42 people and injured at least 239.
The raid marked the fifth bombing attack in Istanbul this year, and struck the country's most important transportation hub. While Kurdish militants have also recently attacked targets in Istanbul, analysts said the operation bore all the hallmarks of Isis.
A senior Turkish official yesterday gave a timeline of the attack: First, a militant detonated explosives in the arrivals area on the ground floor of the international terminal. A second attacker exploded minutes later in the departures area upstairs, the official said. Finally, a third bomber detonated in the parking area amid the chaos and as people fled to escape the attacks inside. It was unclear at what point security forces exchanged gunfire with the attackers, according to the official's timeline. But witnesses spoke of scenes of panic, fear, and wounded fellow travellers.
But even as the country reeled from the violence, the assault on one of the world's busiest airports - and symbol of Turkey's modern economy - threatened to propel the country into a wider war with Isis.
"If the Islamic State is indeed behind this attack, this would be a declaration of war," said Soner Cagaptay, director of the Turkish Research Programme at the Washington Institute for Near East Policy. He said President Recep Tayyip Erdogan "cannot afford to let this go".
Turkey has taken steps to battle Isis, which grew strong amid the bloody civil war in neighbouring Syria. But critics have blasted Turkey for its reluctance to take the fight to the extremists.
For years, Turkish security forces turned a blind eye to the militants that slipped across the border, where mostly Islamist rebels have been battling forces loyal to Syrian President Bashar al-Assad.
Turkey wanted the Syrian leader to step down, and also saw the Sunni rebels as a bulwark against Syria's own autonomy-seeking Kurds. Turkey's ethnic Kurdish population has long sought greater independence from the Turkish state. And the rise of a Kurdish enclave in northern Syria worries nationalist Turks who fear it will inspire the Kurds in Turkey.
Isis has either claimed or been blamed for at least five major suicide attacks in Turkey in the past year. Now, the two sides are edging toward full-fledged conflict, analysts say.
"They went from a Cold War, to a limited war, and are now moving towards full-scale war," Cagaptay said.
But among the questions is whether Turkey, a Nato member and US ally, could actually escalate its role in the campaign in Syria.
Turkey's airstrikes against Isis positions were suspended after Moscow, responding to Turkey's downing of a Russian jet it said was flying over its territory last October, also threatened to shoot down Turkish planes over Syria.
Russia intervened in Syria last fall to prop up Assad in face of a rebel onslaught. Since then, however, Turkey has flown only surveillance and reconnaissance missions in its own airspace. This week, Erdogan met Russian President Vladimir Putin's demand for an apology for the incident.