Istanbul, Turkey (CNN) Gunshots, screams and explosions pierced the air Tuesday as three terrorists armed with bombs and guns killed at least 36 people at Istanbul Ataturk Airport in Turkey.

Witnesses described deadly carnage and crowds in a panic as the attackers struck one of the world's busiest airports.

At least 36 people were killed, Turkish Prime Minister Binali Yildirim said. An additional 147 people were wounded, Turkey's Justice Minister Bekir Bozdag said.

There was no immediate claim of responsibility.

Sue Savage was in the airport to see a friend off when she heard gunshots and then an explosion. More gunshots rang out, followed by another boom, she told "Erin Burnett OutFront."

She ducked into a men's prayer room and then into a men's toilet, where she hid in a stall with a young woman.

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They came out about 30 minutes later, and heard more screams and gunshots. They ducked into a room where luggage is inspected.

She and about 30 people were herded into a women's prayer room until authorities led them out and down an escalator into the main terminal hall.

"There was a lot of blood," she said. The floor was marked with bloody boot marks as the group was led to the other side of the room.

"There was so much glass on the floor they were scuffing it aside so we didn't slip," she said.

Photos: Istanbul airport attacked People flee the scene of a terror attack at Istanbul's Ataturk airport on Tuesday, June 28. Three terrorists armed with bombs and guns attacked the main international terminal, opening fire and eventually detonating their devices. Hide Caption 1 of 22 Photos: Istanbul airport attacked Investigators remove a body after the attack. Hide Caption 2 of 22 Photos: Istanbul airport attacked Police investigators work inside the airport. Hide Caption 3 of 22 Photos: Istanbul airport attacked Turkish special forces secure an area of the airport after the attack. Hide Caption 4 of 22 Photos: Istanbul airport attacked A wounded girl is taken to a hospital in Istanbul. Hide Caption 5 of 22 Photos: Istanbul airport attacked A Turkish police officer directs a passenger at the airport. Hide Caption 6 of 22 Photos: Istanbul airport attacked Travelers embrace outside the airport. Hide Caption 7 of 22 Photos: Istanbul airport attacked One of the bombs was located just outside the international terminal on the pavement, Turkish Justice Minister Bekir Bozdag told CNN. Another was at the security gate at the entrance to the airport. Hide Caption 8 of 22 Photos: Istanbul airport attacked Children and their relatives embrace after reuniting outside the airport. Hide Caption 9 of 22 Photos: Istanbul airport attacked A police officer sets up a security perimeter. Hide Caption 10 of 22 Photos: Istanbul airport attacked People stand outside the airport after the attack. Hide Caption 11 of 22 Photos: Istanbul airport attacked A wounded woman talks on the phone following the attack. Hide Caption 12 of 22 Photos: Istanbul airport attacked Passengers cry as they leave the airport. Hide Caption 13 of 22 Photos: Istanbul airport attacked People on their phones wait with their luggage outside the airport. Hide Caption 14 of 22 Photos: Istanbul airport attacked Workers clear glass debris on the day after the attack. Hide Caption 15 of 22 Photos: Istanbul airport attacked Bullet holes are seen at the airport on Wednesday, June 29. Hide Caption 16 of 22 Photos: Istanbul airport attacked Hide Caption 17 of 22 Photos: Istanbul airport attacked A worker cleans blood from the upper walls of the international departure terminal. Hide Caption 18 of 22 Photos: Istanbul airport attacked A police officer stands guard as a man walks at the airport a day after the attack. Hide Caption 19 of 22 Photos: Istanbul airport attacked A woman cries in Istanbul on June 29. Hide Caption 20 of 22 Photos: Istanbul airport attacked Security personnel scan passengers and employees at a checkpoint on June 29. Hide Caption 21 of 22 Photos: Istanbul airport attacked A worker repairs the airport's damaged ceiling on June 29. Hide Caption 22 of 22

Video from inside the terminal shows people fleeing and the bright orange flash of fire from one of the explosions. Victims stagger and some fall from the blood-covered, slick floor.

Another video shows a man walking with a gun, which he drops when he's apparently shot by a security officer. The man slumps to the ground and the officer briefly stands over him before running. About 10 seconds later, there is an explosion.

Traveler Laurence Cameron described what he saw after he stepped off a plane.

"It was just a massive crowd of screaming people. Some were falling over themselves. A poor chap in a wheelchair was just left, and everyone just rushed to the back of the building, and then people ran the other way and no one really seemed to know what was going on," he told CNN. "Where you normally hail a taxi, that is where the attack happened. The ground is just kind of shredded. There are bloodstains on the floor as well."

Atatürk hava limani bombali saldiri yapildi pic.twitter.com/qWpnLX7sGk — Oguzcan Aksoy (@Oguz146) June 28, 2016

Two bombs in international terminal, official says

Of the three bombers in the airport attack, two were at the international terminal, and the third terrorist was in the nearby parking lot, a Turkish official told CNN. All three detonated suicide vests.

Turkish President Recep Tayyip Erdogan called for a unified international fight against terrorism.

"Make no mistake: For terrorist organizations, there is no difference between Istanbul and London, Ankara and Berlin, Izmir and Chicago or Antalya and Rome," he said. "Unless all governments and the entire mankind join forces in the fight against terrorism, much worse things than what we fear to imagine today will come true."

The attacks happened on a warm summer night at the airport, east of Istanbul, which is the 11th busiest in the world in terms of passenger traffic.

Istanbul Ataturk Airport -- 11th busiest airport in the world (2015) -- Europe's third-busiest airport (2015) -- 62 million passengers passed last year -- There are two main passenger terminals -- Terminal 1: older, smaller, domestic -- Terminal 2: newer, bigger, international -- Vehicle checkpoint at compound entrance -- X-ray checkpoint at terminal entrance Source: Airports Council International/CNN

The airport was closed overnight for several hours, and flights into the airport had been diverted to the capital of Ankara and other cities.

The airport has since reopened, and the U.S. Federal Aviation Administration said it has lifted a ground stop for flights between the United States and the airport.

Prime Minister Yildirim told reporters that the airport was opened for incoming and outgoing flights early Wednesday, according to the semiofficial Anadolu news agency.

Turkish PM: Attack likely from ISIS

"The terrorists came to the airport in a taxi and then carried out their attacks," the Prime Minister said. "The fact that they were carrying guns added to the toll. Preliminary findings suggest all three attackers first opened fire then detonated themselves."

Yildirim didn't clarify why, but said signs pointed to ISIS being behind the attacks. The attacks occurred with a little more than a week left in the Muslim holy month of Ramadan.

Multiple U.S. officials told CNN's Pamela Brown and Elise Labott that the early thinking among U.S. intelligence officials was that ISIS or an ISIS-inspired group was to blame. Like the Turkish Prime Minister, the officials said there is much more investigating to be done.

One official said the attack bears the hallmarks of ISIS because of the target and the method. And a senior US official pointed to the way it was coordinated using weapons and explosions.

Some analysts say that this type of attack is a response to ISIS recent defeats in Iraq and Syria, notably the loss of Falluja.

"They may lose ground, but they're still a potent force," CNN analyst Bob Baer said.

"They know their days in Iraq and Syria are probably numbered, they've got to find somewhere else to operate," said retired Lt. Col. Rick Francona, a former U.S. military attaché in Syria.

It would be a "big surprise" if it was the PKK -- or Kurdistan Workers' Party --- based on how the attack was conducted. The PKK tends to target military and security installations, other officials said.

Terror attacks in Turkey

Turkey has been rocked by a string of terror attacks over the past year as it weathers bombing campaigns by ISIS and Kurdish militants.

As part of the U.S.-led coalition against ISIS, Turkey allows coalition planes to fly raids on ISIS targets in neighboring Iraq and Syria from its territory.

And last year, Turkey resumed hostilities with the PKK, Kurdish militant separatists, after a two-year cease fire broke down.

The PKK has been in an armed struggle with the Turkish government for decades and is considered a terror group by Turkey, the United States and the European Union.

In March, at least 37 were killed when a car bomb detonated near a bus stop in the Turkish capital, Ankara, in an attack claimed by a Kurdish militant group.

Six days later, an ISIS suicide bomber detonated himself on one of Istanbul's main streets, killing four.

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A month earlier, 28 were killed in a blast targeting military vehicles in central Ankara. A Kurdish group claimed responsibility.

And in January, at least 10 German tourists died in a suicide bombing in Istanbul's Sultanahmet Square that Turkish authorities linked to ISIS.

The violence has had an impact on Turkey's tourism industry, a key sector of the national economy.

U.S. expresses condolences, support

Ataturk Airport is "one of the most secure airports in the world," CNN senior law enforcement analyst Tom Fuentes said. But the airport has been "very overwhelmed for several decades with terrorism from PKK."

Experts say Turkey is especially vulnerable because of the terror groups operating there.

"You cannot protect these airports 100% ... especially in a place like Turkey, where ISIS has cells everywhere," said Francona, the former U.S. military attaché in Syria.

The White House issued a statement condemning the terror act.

"Ataturk International Airport, like Brussels Airport which was attacked earlier this year, is a symbol of international connections and the ties that bind us together," it said.

"Our deepest condolences go out to the families and loved ones of those killed, and we wish a speedy recovery to those injured. We remain steadfast in our support for Turkey, our NATO ally and partner, along with all of our friends and allies around the world, as we continue to confront the threat of terrorism."

The U.S. Embassy in Ankara sent consular officers to the airport to see whether any of the victims were from the United States.

There were no immediate indications of any American casualties, a senior State Department official said.