Istanbul: Three explosions hit Istanbul's main international airport on Tuesday, killing dozens of people and injuring more than 100, in the latest in a string of attacks in Turkey's biggest city this year.

The blasts hit Istanbul Ataturk, Turkey's largest airport and a major transport hub for international travellers. Witnesses also reported hearing gunshots. The city's governor said three suicide bombers carried out the attack.  

CCTV from inside Istanbul's Ataturk Airport appears to show one of the attackers. Photo: CCTV/Supplied

Justice Minister Bekir Bozdag said 31 people were killed in the attack and 147 wounded while another senior government official told The Associated Press it could climb much higher.

The senior official at first said close to 50 people had already died, but later said that the figure was expected to rise to close to 50.

An entrance of the Ataturk Airport in Istanbul after explosions. Photo: AP

Pictures posted on social media from the site showed wounded people lying on the ground inside and outside one of the terminal buildings.

The "vast majority" of victims were Turkish nationals but foreigners were also among the casualties, an official said on Wednesday.

Travellers in airport fleeing the blasts, caught on CCTV. Photo: Supplied

An Australian government spokeswoman said the government was aware of the reports. She said the Australian embassy in Ankara and the consulate in Istanbul were working to determine if any Australians had been affected.

Random fire

One of the attackers "randomly opened fire" as he walked through the terminal building, shortly before the explosions, a witness told Reuters.

A woman stands and cries outside Istanbul's Ataturk airport after the explosions. Photo: AP

"We came right to international departures and saw the man randomly shooting," said Paul Roos, 77, a South African tourist on his way back to Cape Town with his wife.

"He was just firing at anyone coming in front of him. He was wearing all black. His face was not masked. I was 50 metres away from him.

"We ducked behind a counter but I stood up and watched him. Two explosions went off shortly after one another. By that time he had stopped shooting," Mr Roos said.

A police cordon is set up outside Istanbul's Ataturk airport. Photo: AP

"He turned around and started coming towards us. He was holding his gun inside his jacket. He looked around anxiously to see if anyone was going to stop him and then went down the escalator ... We heard some more gunfire and then another explosion, and then it was over."

Australian travellers

Australian woman Sara Bosz, 31, who has been travelling through Turkey for the past 12 days, was woken by scared travellers in her Istanbul hotel just after midnight local time, shortly after news broke of the blasts at the airport. 

A passenger's blood pressure is checked by health officials outside Istanbul Ataturk after the attack. Photo: Getty Images

"The other travellers were obviously very scared. They came knocking at my door. 

"I'm just trying to help them and reassure them, among my own fears as well, that everything is going to be OK. 

"We're so very fortunate that none of us were travelling or flying out tonight."

An assault weapon on the floor after the attack. Photo: Twitter/@arabthomness

Steph Sinclair, 24, a journalist from Perth who has been travelling in Turkey with her boyfriend, Beau Vaux, for the past 10 days, was due to fly from Ataturk Airport just hours after the attack.

Describing herself as "a bit shaken", Ms Sinclair said the couple had been returning from dinner late on Tuesday when their taxi driver had told them about the bomb blast, which happened shortly after 10pm.

They had already booked a taxi for 4am on Wednesday for their 6.55am flight.

"Certainly it's a bit close for comfort. We're feeling really lucky that we were booked on the later flight and just sad for the people that are suffering," she said.

They couple had wavered on whether to go ahead with a Turkey visit because of previous attacks but eventually decided to go, Ms Sinclair said.

"It's been really quiet. Tourism has really suffered from all the terror threats," she said.

Australians Steph Sinclair and Beau Vaux learned about the attack the night before they were due to fly out of Istanbul. Photo: Steph Sinclair

Attacker wrestled

One witness told CNN Turk that gunfire was heard from the car park at the airport. Taxis were ferrying wounded people from the airport, the witness said.

One witness said he saw a police officer wrestle a suicide bomber to the ground, the attacker then detonated his bomb, according to an NBC reporter based in Istanbul.

The state-run TRT television said an explosion hit a control point at the international arrivals terminal of the airport.

Witness Ercan Ceyhan told CNN-Turk that he saw about 30 ambulances enter the airport.

The private DHA news agency said the wounded, among them police officers, were being transferred to Bakirkoy State Hospital.

Some flights to Ataturk Airport have been diverted, an airport official said, adding it was not clear what flights would be cancelled on Wednesday morning.

Australian reaction

Prime Minister Malcolm Turnbull responded to the attack by strongly reaffirming Australia's intention to continue fighting the Islamic State group militarily in the Middle East.

"We will continue to work with our allies in the Middle Eastern theatre to destroy ISIL or Daesh in the theatre, in the field. That is a critical military objective. And as you know, Australia has one of the largest contributions to that multinational effort. We will continue to do that."

Mr Turnbull offered "our very deepest sympathies and condolences to the people of Turkey who have been hit with a series of suicide bombings in recent times".

"This is a reminder that Islamist terrorists seek to destroy, divide and kill Muslims as well as Christians and other people of non-Muslim faiths. They are a murderous, criminal movement seeking to create division and destruction and make us turn on each other," he said.

He added that Australia and Turkey had a "common bond" through their shared Gallipoli history and that "many Australians are very familiar with the airport at Istanbul".

Foreign Affairs Minister Julie Bishop has issued a statement condemning "what appears to be a co-ordinated terror attack" and said the government is "urgently seeking" to determine whether any Australians have been caught up in the attack.

"Our thoughts and sympathies are with the people of Turkey," she said. "I understand the Turkish authorities have secured the area of the attack and have advised that Ataturk Airport will be closed for up to 48 hours."

She said the Department of Foreign Affairs and Trade's travel advice for Turkey continues to advise Australian travellers to "reconsider their need to travel to Istanbul" – a warning that has been in place since late March in response to previous attacks.

People concerned about loved ones should try to contact them directly, she said. But if they're unable to reach them and are worried about their welfare they can call the 24 hour Consular Emergency Centre on 1300 555 135 or +61 2 6261 3305 if they are calling from overseas.

Islamic State blamed

Dogan News Agency cited police sources as saying: "ISIS is behind the attack". A Turkish official, however, said it was too early to confirm any links when asked about the Dogan News Agency report. ISIS and ISIL are other terms for Islamic State.

Governor Vasip Sahin has told local broadcaster NTV that three suicide bombers carried out Tuesday's attack.

Officials had previously said one or two attackers had blown themselves up at the entrance to the international terminal at the airport after police fired at them.

Police fired shots to try to stop the attackers just before they reached a security checkpoint at the arrivals hall of the airport but they blew themselves up, one of the officials said.

Frequent bombings

Turkey has suffered a spate of bombings this year, including two suicide attacks in tourist areas of Istanbul blamed on Islamic State, and two car bombings in the capital, Ankara, which were claimed by a Kurdish militant group.

In the most recent attack, a car bomb ripped through a police bus in central Istanbul during the morning rush hour, killing 11 and wounding 36 near the main tourist district, a major university and the mayor's office.

Turkey, which is part of the US-led coalition against Islamic State, is also fighting Kurdish militants in its largely Kurdish south-east.

US President Barack Obama was briefed on Tuesday about the explosions by Lisa Monaco, his homeland security and counterterrorism adviser, the White House said.

Clinton, Brussels respond

US Democratic presidential candidate Hillary Clinton said the attack was a reminder that the United States "cannot retreat".

"Today's attack in Istanbul only strengthens our resolve to defeat the forces of terrorism and radical jihadism around the world," she said in a statement.

"We must deepen our co-operation with our allies and partners in the Middle East and Europe to take on this threat."

Officials at the Brussels Airport, the scene of a deadly suicide attack in March that killed 32, also tweeted their condolences.

Arnaud Feist, chief executive of Brussels Airport Company, tweeted that he was "deeply moved" to learn of the attacks.

"Our thoughts are with the victims, their family & friends. Strength to our colleagues."

Reuters, AP, Fairfax Media, Lisa Visentin, David Wroe, Chris Zappone

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