Police have detained five suspected Islamic State group militants believed to be linked to the deadly Istanbul nightclub attack.
The state-run Anadolu Agency said the operation was launched in the Aegean port city of Izmir on Wednesday, and is continuing.
The gunman who killed 39 people during new year celebrations has not been publicly named and is still at large.
The so-called IS group has claimed responsibility for the attack, which also wounded nearly 70 people.
Foreign minister Mevlut Cavusoglu said authorities had identified the gunman, but gave no further details.
Most of those killed were foreigners from the Middle East.
The private Dogan news agency said the police operation targeted three families who had arrived in Izmir about 20 days ago from Konya – a city in central Turkey where the gunman is thought to have been based before carrying out the attack.
It said 27 people, including women and children, were taken into custody.
At least 14 people had previously been detained in connection with the attack, including two foreigners stopped on Tuesday at the international terminal of Istanbul’s Ataturk Airport after police checked their phones and luggage, according to Anadolu.