Story highlights Authorities detain 20 alleged members of ISIS in connection with Sunday's attack

ISIS claimed responsibility on Twitter, but CNN can't independently verify it

Istanbul (CNN) Turkish authorities said Wednesday they have identified the gunman who killed 39 people in the New Year's nightclub terror attack in Istanbul.

Turkish Foreign Minister Mevlut Çavusoglu announced the development but did not name the suspect or provide his nationality.

Authorities have also detained 20 alleged members of ISIS in connection with Sunday morning's attack at the Reina nightclub , state-run news agency Anadolu reported Wednesday.

Counterterrorism officers arrested the suspected militants at four addresses in the Bornova and Buca districts of the Aegean province of Izmir, according to Anadolu. Eleven women were among those arrested.

Anadolu said those detained are thought to have lived with the attacker in the central Anatolian city of Konya.

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