Sahin said he regarded the assault on one of the city’s best known clubs, in which 40 people were also injured, as terrorism.
ABC reported between 500 and 600 people were thought to have been in the club when the attack happened at around 1:15 a.m. local time.
The attackers were believed to have entered the nightclub dressed as Santa Claus, private NTV television reported earlier, according to ABC.
"A terrorist with a long-range weapon… brutally and savagely carried out this incident by firing bullets on innocent people who were there solely to celebrate the New Year and have fun," Sahin told reporters at the scene, ABC reported.
“One person first kills the police officer outside, and then a civilian,” the governor said, according to a story posted by the New York Times. “Inside, he rained bullets brutally, mercilessly over innocent people who were there just to celebrate the New Year and have fun.”
Police were still searching for the attackers.
Turkey witnessed the bloodiest coup attempt in its political history on July 15, 2016, when a section of the Turkish military launched a coordinated operation in several major cities to topple the government and unseat President Recep Tayyip Erdogan.
Soldiers and tanks took to the streets and a number of explosions rang out in Ankara and Istanbul.
Turkish fighter jets dropped bombs on their own parliament, while the chairman of the Joint Chiefs of Staff, Hulusi Akar, was kidnapped by his own security detail.
For several hours, it looked like Turkey was going to face the fourth devastating military coup in its 95-year political history.
But at this point, something unprecedented happened.
As news of the coup attempt spread via social media, thousands of ordinary citizens, armed with nothing more than kitchen utensils, gathered in streets and squares around Anatolia to oppose the coup.
The crowds resisted tank fire and air bombardments and, with the help of loyalist soldiers and police forces, they defeated the coup attempt in a matter of hours. The government swiftly declared victory and scores of troops that had taken part in the coup surrendered on the Bosphorus Bridge in Istanbul.
Yet the overall price of victory was high: 241 people were killed and 2,194 others were injured.
EDITOR’S NOTE: Al Jazeera of Al Jazeera, Doha, Qatar (TNS) contributed to this article.