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.
Anadolu also reported that an array of military hardware was discovered during the raids, including night-vision equipment, a sniper scope, an ammunition belt and other items. Twenty children found at the addresses were taken into temporary care.
Altogether, at least 36 people are being held in connection with the nightclub shooting, though the gunman who carried it out
remains at large.
ISIS claimed responsibility for the attack in a statement posted to Twitter, but CNN cannot independently verify it. The terror group boasted of carrying out the first major terrorist attack of 2017.
Suspect seen in selfie video
The "selfie video" featuring the man in Istanbul's Taksim Square was first posted on a pro-ISIS Telegram account before Turkish media broadcast it, said Laith Alkhouri, a director at Flashpoint, an American business risk intelligence company tracking terrorist and cyber threats.
Alkhouri told CNN that such a release suggests the attacker was part of a network supportive of or linked to ISIS, and that he had shared the selfie footage with the terror group before or after the attack.
On Tuesday, Interior Minister Suleyman Soylu told lawmakers that Turkish security forces had prevented 339 major terror incidents in 2016 -- 80 of which came in the final three months of the year.
In his speech to parliament, Soylu cited attacks launched by the militant Kurdistan Workers' Party, or PKK, as well as those by Daesh, the Arabic term for ISIS.
Anadolu quoted Soylu
as saying that "313 of the incidents were planned by PKK, 22 by Daesh and four by radical leftist groups."
He said that 247 improvised explosives and 61 bomb vehicles had been seized in 12 months.
He also revealed the capture of 23 suicide bomber suspects as well as 42 terrorist group members who were preparing for attacks.
Both ISIS and Kurdish militants have launched attacks in Turkey, which is reeling from a failed military coup in July.
On Wednesday, Anadolu reported that authorities arrested four people, including a woman, in connection with a December 17 car bombing that killed 13 soldiers
and wounded dozens in the central city of Kayseri.
Victims from 14 countries
At least 11 victims in this week's attack
on the upscale nightclub were from Turkey, according to Anadolu, while at least 27 victims hailed from 13 other countries, including Lebanon, Iraq, Syria and Canada.
Dozens of people were hospitalized. A handful of the injured were in critical condition.
Witnesses described how the New Year's Eve celebration turned into a bloodbath.
"We were having fun. At first we thought it was a fight, then there was a lot of gunfire," Yunus Turk told CNN.
"After the gunfire, everyone started to run toward the terrace. We ran as well. There was someone next to me who was shot and fell on the floor. We ran away and hid under the sofas."