Turkish police detained five suspected Islamic State group militants Wednesday in connection with the deadly Istanbul nightclub attack, Turkey’s state-run news agency reported.

The Anadolu Agency said the arrests took place in the Aegean port city of Izmir.

The chief suspect, who killed 39 people during New Year’s celebrations, has not been publicly named and is still at large.

The Islamic State group has claimed responsibility for the attack, which also wounded nearly 70 people. Anadolu said the number of arrests was expected to rise as the manhunt goes on.

At least 14 people were previously detained in connection with the attack, including two foreigners stopped Tuesday at the international terminal of Istanbul’s Ataturk Airport after police checked their cellphones and luggage, according to Anadolu.

The private Dogan news agency said the main suspect arrived in Turkey from Syria with his wife and two children. The gunman is believed to be about 25 years old and from a Central Asian nation such as Uzbekistan or Kyrgyzstan. Selfie video footage of him in central Istanbul emerged Tuesday.

Turkey's Foreign Minister Mevlut Cavusoglu said the identity of the killer had been determined but gave no further details.

Turkey has extended for another three months a state of emergency that was implemented after a failed coup in July.

Turkey’s President Recep Tayyip Erdogan said in an address Wednesday that "in Turkey, no one’s way of life is under any threat. Those who claim this have to prove it. It is my duty to protect everyone’s rights." Erdogan was responding to accusations that his government has not done enough to counter terrorism threats.