Turkish authorities say that they suspect the Islamic State's involvement in Tuesday's terrorist attack on Istanbul's Ataturk Airport.
Heavily armed men first opened fire indiscriminately, and then blew themselves up, killing 42 and wounding another 239.
Turkish President Tayyip Erdogan called this attack a "turning point" for the world to fight against terrorism.
"I hope that the Ataturk Airport attack, especially in Western countries [and] all over the world, will be a milestone for the joint fight against terrorist organizations, a turning point," he said.
Interior Minister Efkan Ala said that investigations pointed to the role of IS, but there was no decisive evidence leading up to that.
"Every connection is being evaluated carefully," he added.
After Ala's statement, Prime Minister Binali Yildirim said on television that IS' role in the attacks was likely.
"Our thought that it is Daesh (Islamic State) continues to gain weight," he said.
Three terrorists attacked the busy airport, and one of them opened fire on the outside of the airport while two of them made their way inside. One of them went to the departure hall, and the second in arrivals. All three of them blew themselves up.
"When the terrorists couldn't pass the regular security system, when they couldn't pass the scanners, police and security controls, they returned and took their weapons out of their suitcases and opened fire at random at the security check," said Yildirim.
The president condemned the attack, and said the attack exposed the true nature of terrorism.
"It is clear that this attack is not aimed at achieving any result but only to create propaganda material against our country using simply the blood and pain of innocent people," Erdogan said.
"Today's bombs in Istanbul [have demonstrated] the treacherous nature of terrorism. It could happen in any city in the world, in any airport."
The office of the Prime Minister officially declared Wednesday a national day of mourning for the victims of the attack.
Turkey is a key partner with the US and allies fighting the Islamic State, and shares a long border with Syria and Iraq where the Islamic State holds large portions of the land.
In March this year, five people were killed on a street by a Turkish national affiliated with Islamic State, who blew himself up. Earlier in January, IS killed about 12 German citizens who were touring the country.
In October 2015, a twin bombing attack killed 103 people at a peace rally near one of Ankara's train stations. Nobody took the responsibility for the attack, but Turkish government said that Islamic State was behind it.
On March 22, two suicide bombings by IS at Brussels airport killed 16 people, and another attack the same day at a Brussels subway station claimed another 16 lives.