At least 35 people were killed and 40 wounded Sunday when two gunmen dressed as Santa stormed a popular Istanbul nightclub and opened fire in what the city's governor called a "terror attack".
"Unfortunately, at least 35 of our citizens lost their lives. One was a police officer," Vasip Sahin told reporters at the scene of elite Reina nightclub on the Bosphorus in the city's European side.
"Forty people are receiving treatment in hospitals," Sahin added, describing the incident as a "terror attack".
Dogan news agency said two gunmen had entered the venue dressed as Santa firing shots at random.
Many party-goers threw themselves into the Bosphorus in panic after the attack and rescue efforts were in progress to save them from the waters, NTV television said.
Dogan news agency reported that some witnesses claimed the attackers were "speaking Arabic" while NTV broadcaster said special force police officers were searching the nightclub.
TV images showed the scene cordoned off by police officers.
According to Dogan, there were at least 700 revellers celebrating the start of 2017 after a bloody 2016 in Turkey.
The attack comes less than a month after the twin blasts outside the Istanbul stadium of top Turkish team Besiktas on December 10 killed 44 people claimed by Kurdish militants.
The city suffered multiple terror attacks last year at the hands of Islamic State jihadists and Kurdish rebels.
Amid fears of another attack in Istanbul, at least 17,000 police officers were deployed in the city for New Year's Eve celebrations.
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