"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," Vasip Sahin told reporters, according to the BBC.
Initial reports said there were two or more attackers involved in the act of terrorism that has killed 39 and injured at least 69.
Witnesses say the gunman or gunmen were speaking Arabic.
Sahin said the gunman killed a police officer and a civilian outside the club before firing on the crowd inside at around 1:45 a.m. There may have been as many as 800 people inside, local media are reporting. Revelers even jumped into the Bosphorus to escape the hail of bullets, according to social media reports.
The following footage is said to be from a security camera inside the club.
Turkish police have now cordoned off the club, local media report. According to Turkey's Hurriyet newspaper, security forces are also patrolling the Bosphorus Strait near the site of the attack.
#Turkey Footage near #İstanbul nightclub, where gunfire was reported. Turkish TV says there are injured people pic.twitter.com/D6Sesl9xfd
— Rosy (@rose_k01) December 31, 2016