Dozens were killed after three suicide bombers blew themselves up at Turkey's largest airport, Istanbul Ataturk, on Tuesday.
The Associated Press, citing senior Turkish officials, said that nearly 50 people have died.
The attack, which occurred at around 10 p.m. local time and appeared to be coordinated, left at least 60 others injured, according to Turkey's state-run Anadolu Agency.
The "vast majority" of victims were Turkish nationals, Reuters reported, but foreigners were also among the casualties, the wire service said, citing an official on Wednesday.
The Associated Press said that initial indications suggest that ISIS is responsible for the attack.
"The assessments show that three suicide bombers carried out the attacks in three different spots at the airport," Vasip Şahin, Istanbul Province's governor, said.
The suspects apparently detonated the explosives at the security check-in at the entrance to the airport's international terminal as they exchanged gunfire with police, a Turkish official told Reuters.
Turkish Justice Minister Bekir Bozdag said that at least one of the attackers opened fire on the crowd using a Kalashnikov rifle before detonating himself.
It is still unconfirmed who is responsible for the attack, but ISIS and Kurdish groups have claimed multiple attacks in Turkey in the last year. The Kurdistan Workers' Party (PKK) is waging an insurgency against the Turkish government, but primarily targets military and security personnel in the country's southeast.
The Ataturk attack "fits the ISIS profile, not PKK," a counterterrorism official told CNN, adding that the PKK doesn't usually go after international targets.
Some flights to the airport have been diverted, an airport official told Reuters.
Ataturk is the 11th-busiest airport in the world, with at least 61 million travelers passing through in 2015. Many have noted that Turkey had assigned extra security to the entrance of Ataturk in the wake of numerous ISIS-linked terrorist attacks in Istanbul in the past several months.
Airport-security workers recorded the surveillance-camera footage of the moment the explosion ripped through the airport:
— Conflict News (@Conflicts) June 28, 2016
Footage has emerged of panicked travelers running away from the scene of the explosions:
— Jon Williams (@WilliamsJon) June 28, 2016
Lisa Monaco, assistant to the US president for homeland security and counterterrorism, has briefed US President Barack Obama on the attack, according to a White House official.
All scheduled flights in both directions between the US and Istanbul have been temporarily suspended, a senior US official told ABC. The airport will be closed until 8 p.m. on Wednesday local time.
The US State Department renewed its three-month-old travel warning for Turkey on Monday, noting that "Foreign and US tourists have been explicitly targeted by international and indigenous terrorist organizations," in a warning posted on the department's website.
The US consulate is working to determine if US citizens are among the airport attack's victims, the State Department tweeted.
Many passengers are now stranded outside of the airport:
Huge numbers of passengers stranded outside Ataturk pic.twitter.com/E5w4jRJI9N
— Borzou Daragahi (@borzou) June 28, 2016
ISIS has claimed responsibility for multiple terrorist attacks on Turkish soil since mid-2015.
In January, 13 people were killed and 14 injured in a suicide bombing in a popular central square in Istanbul. The perpetrator was identified as Nabil Fadli, an ISIS follower from Syria.
Last July, ISIS claimed responsibility for a suicide bombing in southeastern Turkey that killed 33 young activists. Three months later, a n ISIS-linked suicide bombing at a peace rally in Ankara killed over 100 people.
Michael Weiss, co-author of "ISIS: Inside the Army of Terror," noted on Twitter that ISIS has a "lot of motives for attacking Ataturk airport, including the imminent loss of Manbij [in Syria], Turkish shelling of ISIS, and of course Turkish-Israel rapprochement."
The Kurdistan Freedom Falcons — a breakaway faction of the PKK — claimed responsibility for a suicide bombing in Ankara in February that killed 29 people and another in March that killed 37. A car bomb claimed by Kurdish separatists ripped through a police bus in central Istanbul on June 7 during the morning rush hour, killing 11 people and wounding 36 near the main tourist district, a major university, and the mayor's office.