Turkish officials have raised the casualty figures from June 28 attack on Istanbul's Ataturk International Airport to 41 killed and 239 injured.
The majority of those killed were Turkish citizens, while at least 12 of those killed were foreign nationals and three held dual nationality.
Turkish officials said three suicide bombers arrived at the airport by taxi and blew themselves up at the entrance, near the security check-in area, after an exchange of gunfire with police.
Turkish Justice Minister Bekir Bozag said there were also signs of an explosion near the subway station at the airport.
Video footage showed one of the attackers inside the terminal being shot, apparently by a security-service member, before hitting the floor as people ran away from him.
But the attacker then blew himself up some 20 seconds later.
With similarities to the Brussels airport bombings in March, Turkish Prime Minister Binali Yildirim said initial indications are the Islamic State extremist group was responsible.
President Recep Tayyip Erdogan has 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."
U.S. President Barack Obama told Erdogan via phone on June 29 that the United States will offer "any support that the Turks can benefit from as they conduct this investigation and take steps to further strengthen the security situation in their country," Obama's spokesman said.
Russian President Vladimir Putin, in a call to Erdogan on reviving bilateral relations, also expressed his condolences to Erdogan over the airport attack.
Meanwhile, Iyad Madani, the secretary-general of the Organization of Islamic Cooperation (OIC), stressed his "absolute rejection" of the attack and called for international cooperation to stop "terrorism by addressing its causes and various contexts."
There are 57 countries in the OIC, including Turkey.
PHOTO GALLERY: Death, Chaos In Istanbul
Among those wounded in the attack, 109 have already been discharged from hospitals, the Istanbul governor's office said.
But 41 with serious injuries are reportedly still in intensive care in Istanbul hospitals.
Six Saudis and two Iraqis were among the dead, a Turkish official said.
Citizens from China, Jordan, Tunisia, Uzbekistan, Iran, and Ukraine were also among the foreigners killed.
The attack on Europe's third-busiest airport was the deadliest in a series of suicide bombings this year in Turkey, many blamed on Kurdish militants.
In Washington, CIA Director John Brennan said on June 29 that the way the Istanbul attack was carried out leads him to believe it was done by IS militants.
He said the attack "bears the hallmarks of [IS's] depravity."
Brennan also warned that such an attack by IS members was also possible in the United States.
Ataturk airport resumed full operations earlier on June 29 after being closed for several hours after the attack.
The United States temporarily stopped all flights to and from Istanbul, one of Europe's busiest airports.
Turkey has been hit by a string of deadly attacks in recent months, blamed on both Kurdish rebels and Islamic State militants.
ACI Europe, the European airports association, said airport security was increased across Europe after attacks at the airport in Brussels in March, but it said many of the deaths in Istanbul were of people lined up near X-ray machines for security checks at the terminal's entrance.
"We must face the reality that when dealing with a terror threat based on suicide bombing, no security measures can ensure 100 percent protection," ACI Europe said in a statement.