ANKARA (AFP) - Turkey on Thursday detained 13 suspected Islamic State in Iraq and Syria (ISIS) militants over the deadly Istanbul airport attack, as chilling details emerged of how suicide bombers launched their assault.

The death toll from Tuesday's gun and suicide bomb spree at Ataturk airport has risen to 44, state-run news agency Anadolu said, with more than 200 people injured.

Nineteen foreigners are among the dead, the interior minister said.

Authorities have identified the bombers as a Russian, an Uzbek and a Kyrgyz national.

Turkey has been plunged into mourning over the carnage at Ataturk airport, the deadliest of several attacks to strike Turkey's biggest city this year.

Police carried out more than a dozen raids across Istanbul early Thursday, arresting 13 people including four foreigners, Interior Minister Efkan Ala said.

Turkey has suffered a string of deadly attacks in the past year blamed on either ISIS or Kurdish rebels, and the airport attack comes just at the start of the crucial summer tourist season.

Ala told reporters late Wednesday there was an ongoing "serious and comprehensive investigation" into who was behind the attack.

Using another name for ISIS, he said: "First signs point to Daesh, but it's not certain yet."

CIA director John Brennan also said the assault bore the "hallmark" of the militant group.

There has been global condemnation of the attack, with the Eiffel Tower set to glow in the red and white of the Turkish flag on Thursday night.

Details are emerging of how the attackers arrived at Turkey's busiest airport by taxi before indiscriminately firing at passengers with automatic rifles and detonating suicide bombs.

"The terrorists failed to pass through the regular security system, scanners and police control," Prime Minister Binali Yildirim told reporters late on Wednesday.

"They returned and came back with long-range rifles they took out from their suitcases, and passed the security control by opening fire randomly at people," he said.

"One of them blew himself up outside and the other two took advantage of the panic during the opening of the fire, entered inside and blew themselves up."

A senior source close to the presidency gave a slightly different version of events, saying two attackers blew themselves up inside the airport before the third followed suit outside.

CCTV footage widely-circulated on social media showed a huge ball of flame erupting at the entrance, scattering terrified passengers.

Another video showed a black-clad attacker running inside the building before collapsing to the ground - apparently felled by a police bullet - and blowing himself up.

The dead include three Saudis, a Chinese national, a Tunisian and a Ukrainian.

The Turkish victims included four members of the Amiri family - three women and a nine-year-old girl, Huda, whose joint funeral was attended by hundreds in Istanbul on Thursday.

Living in Saudi Arabia, they were coming back for a holiday to mark the Muslim holy month of Ramadan when the bombers struck.

Authorities are under pressure to convince visitors that Turkey is still safe, as the vital tourism industry has taken a heavy hit from a string of deadly attacks in the past year.

Ege Seckin, an analyst at IHS Country risk, said the attack was "most likely conducted by the Islamic State to undermine the Turkish economy by attacking the airport ahead of the summer months, when tourism peaks".

Yildirim said Turkey would "increase the presence of specially-trained staff" at the nation's airports.

He moved swiftly after the bombings to deny there had been any lapse in security, but many Turks have been angered by the perceived failure to stop the bombings.

"It was an airport," one man could be heard shouting outside an Istanbul morgue on Wednesday, as devastated families went to collect the bodies of loved ones.

"It's not like this happened in the street."

Turkey has suffered at least five attacks blamed on ISIS militants, including a blast in Ankara in October that left over 100 dead, the worst in the country's modern history.

In January, a bombing in the heart of Istanbul's tourist district, also blamed on ISIS, killed a dozen German visitors.

Two months later, three Israelis and an Iranian were killed in another attack attributed to the militants on the city's main Istiklal shopping street.