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A Tunisian victim of a suspected Islamic State group attack that killed 42 in Istanbul's airport was in the country to secure the release of his son, detained for joining the militant organisation, diplomats suggested on Wednesday.

Fathi Bayoudh, a doctor who had been in Turkey for several weeks attempting to release his son from prison, was killed in the deadly suicide bombings that rocked the international airport.

His son is accused of joining the militant group in Syria, a foreign ministry source was quoted as saying by a local Tunisian radio station.

The Tunisian consulate in Istanbul had been in contact "with the Bayoudh family since December", according to the head of consular affairs at Tunis' foreign ministry, Faycal Ben Mustapha.

"It was to do with their son. We don't know exactly what he did, but he went to Iraq and then Syria and ended up in detention in Turkey," he said.

A defence ministry spokesman confirmed a Tunisian who was in Turkey on private business had been killed in Tuesday's attack, but fell short of specifying the details of the visit.

But Bayoudh allegedly travelled between the two countries for months attempting to persuade his son to return home with him, an anonymous government source told AFP.

No group has yet claimed the attack, however, officials - including the chief of the US Central Intelligence Agency - pointed fingers towards the Islamic State group, stating the attack bears the "hallmark" of the militant group.

"The despicable attacks in Istanbul International Airport yesterday that killed dozens and injured many more certainly bears the hallmark of [IS'] depravity," Brennan said.

The attack appeared to be well coordinated and ruthless.

Militants fired indiscriminately into crowds of passengers before blowing themselves up at the entrance of the airport, one of the busiest flight hubs in Europe.