Update: US President Barack Obama spoke on Wednesday with Turkish President Tayyip Erdogan about the attack at Istanbul's main airport, offering assistance to the Turkish government in its investigation, the White House said.
In a telephone call, Obama expressed his condolences over Tuesday's shootings and suicide bombings at the airport, which killed 41 people and wounded 239, White House spokesman Josh Earnest said.
Earnest declined to offer any official US assessment of who might have been responsible for the bombing.
"Any information that we obtain that could be useful to the Turkish investigation we certainly will share that information, but I don't have any information that we've obtained that I can discuss publicly at this point," Earnest told reporters during a briefing.
The militant group Daesh is at the top of the list of suspect for the attack, according to two US counterterrorism officials familiar with the early stages of investigations.
Earnest did not name any suspects in the Turkey bombing, but he said that the United States remains concerned about Islamic State's ability to carry out attacks.
Triple suicide bombing
A triple suicide bombing at Istanbul's international airport left 41 people dead, 13 of them foreign nationals, and 239 wounded, the city governor said in a statement.
The governor's office said 109 of the 239 wounded were discharged from hospital.
It said 13 of the dead were foreigners.
A Turkish official, speaking on condition of anonymity, said five of the dead were from Saudi Arabia, two were from Iraq, and one from Tunisia, Uzbekistan, China, Iran, Ukraine and Jordan,
No one has claimed Tuesday's attack yet but Turkish authorities said they suspect Daesh militants.
Turkey remains on high security alert after a series of attacks on its soil blamed not only on the Daesh group but also Kurdish militants.
Daesh has never claimed an attack in Turkey. But authorities have blamed the grouo for several attacks, including a blast in Ankara in October 2015 that left over 100 people dead and an attack on Istanbul's busy tourist district Istiklal Street which killed three Israelis and an Iranian.
The attackers began spraying bullets at the international terminal entrance before blowing themselves up at around 10pm (1900 GMT) Tuesday, Turkish authorities said.
It is the deadliest of four attacks to rock Turkey's biggest city this year, with two others blamed on IS and another claimed by a militant Kurdish group.
Though there was no immediate claim of responsibility for Tuesday's carnage, "the evidence points to Daesh", Prime Minister Binali Yildirim told journalists at the scene.
He said the dead included foreigners, but gave no further details.
Forensic experts work outside Turkey's largest airport, Istanbul Ataturk, Turkey, following a blast, June 28, 2016. (Reuters)
Justice Minister Bekir Bozdag put the number of wounded at 147.
The attack prompted the suspension of all flights at the airport -- one of Europe's busiest hubs.
Turkish President Recep Tayyip Erdogan called for an international "joint fight" against terror, as Western allies including the United States condemned the "heinous" attack.
Yildirim said the suicide bombers had arrived in a taxi and opened fire on passengers with automatic rifles before blowing themselves up.
Security camera footage widely circulated on social media appeared to capture two of the blasts.
In one clip a huge ball of flame erupts at an entrance to the terminal building, scattering terrified passengers.
Another video shows a black-clad attacker running inside the building before collapsing to the ground - apparently felled by a police bullet - and blowing himself up.
Tuesday's attack follows coordinated IS suicide bombings at Brussels airport and a city metro station in March that left 32 people dead.
'I can't find my sister'
An injured woman covers her face as she is carried by paramedics into ambulance at Istanbul Ataturk airport, Turkey, following a blast June 28, 2016. (Reuters)
An AFP photographer saw bodies covered with sheets at the terminal, which bore heavy damage from the blasts.
Bullet holes peppered the windows and shattered glass lay on the floor, while abandoned luggage was scattered everywhere.
Hundreds of police and firefighters including forensic officers were at the scene.
"Somebody came and shot at us and then my sister was running," Otfah Mohamed Abdullah told AFP.
"I don't know which way she was running and after that I was falling down. I was on the ground till he finished... I can't find my sister."
There was panic at the nearest hospital in Istanbul's Bakirkoy district, which was inundated with relatives desperate for news of loved ones.
Brussels airport, itself the scene of suicide bombings just months ago, tweeted condolences, saying: "Our thoughts are with the victims of the attacks at @istanbulairport."
Security expert Abdullah Agar told CNN Turk the attack bore the hallmarks of the Islamic State group.
"It really bears a resemblance to their methods," he said in reference to the Brussels bombings, which were claimed by Daesh.
The US and French consulates warned people to stay away from the area.
Erdogan met with his prime minister and military chief after news of the carnage broke.
"We urge the world, especially Western countries, to take a firm stand against terrorism," Erdogan said in a statement.
"Despite paying a heavy price, Turkey has the power, determination and capacity to continue the fight against terrorism until the end."
Istanbul, a major tourism hub that is home to some 15 million people, has suffered a series of attacks in recent months, including a bombing in the heart of the tourist district that killed a dozen German visitors and was blamed on IS.
Two months later, four were killed in a bombing on the city's main Istiklal shopping street, also blamed on Daesh.
A blast on the tarmac at Istanbul's other international airport, Sabiha Gokcen, killed a cleaner in December.
Turkey has been hit by at least five attacks blamed on IS, including a blast in Ankara in October 2015 that left over 100 dead, though the group has never formally claimed responsibility for an attack in Turkey.
Ankara has meanwhile launched a sustained offensive against the outlawed rebel Kurdistan Workers' Party (PKK) following the collapse of a ceasefire last year.
Hundreds of members of the Turkish security forces have since been killed in PKK attacks.