Police in Turkey have conducted a series of raids in Istanbul neighbourhoods, targeting suspects from the so-called 'Islamic State' group after the assault on Ataturk Airport which killed 42 people.
The Anadolu Agency said police searched residences in the Pendik, Basaksehir and Sultanbeyli neighbourhoods, but it was not clear if any arrests were made.
Authorities have blamed 'IS' for Tuesday's co-ordinated attack on one of the world's busiest airports and on a key Nato ally which plays a crucial role in the fight against the terror group.
Although the attack took a heavy toll, including more than 230 injured, the assailants were initially thwarted by extensive security on the airport's perimeter, Turkish officials said.
"When the terrorists couldn't pass the regular security system, when they couldn't pass the scanners, police and security controls, they returned and took their weapons out of their suitcases and opened fire at random at the security check," prime minister Binali Yildirim said.
One attacker detonated his explosives downstairs at the arrivals terminal, one went upstairs and blew himself up in the departure hall, and the third waited outside for the fleeing crowd and caused the final lethal blast, two Turkish officials said.
As the chaos unfolded, terrified travellers were sent running, first from one explosion and then another.
Airport surveillance video showed a panicked crowd of people, some rolling suitcases behind them, stampeding down a corridor, looking fearfully over their shoulders.
Other surveillance footage posted on social media showed one explosion, a ball of fire that sent terrified passengers racing for cover.
Another showed an attacker, felled by a gunshot from a security officer, blowing himself up seconds later.
Investigators later found a Kalashnikov assault rifle, a handgun and two grenades on the bodies, according to the state-run Anadolu news service.
Raids at two addresses uncovered encrypted organisational documents and computer files, the agency said.
There was no immediate claim of responsibility by 'IS', which did not mention the bloodshed on its social media sites.
But an infographic released to celebrate the second anniversary of its self-proclaimed caliphate claimed to have "covert units" in Turkey and other countries.