ISIS group said in a statement the attack on Reina night club in central Istanbul was carried out by “a heroic soldier,” the BBC reports.
At least 600 revellers were celebrating in the early hours of Sunday at Istanbul’s Reina nightclub when the gunman began firing indiscriminately.
ISIS has been blamed for recent attacks in Turkey, which is taking military action against the group in neighbouring Syria.
The militant group has already been linked to at least two attacks in Turkey last year.
The ISIS statement accused Turkey of shedding the blood of Muslims through “its air strikes and mortar attacks” in Syria.
More details of the nightclub attack have been emerging. The gunman, who fired up to 180 bullets, arrived by taxi before rushing through the entrance with a long-barrelled gun he had taken from the boot of the car.
The attacker fired randomly at people in an assault lasting seven minutes, starting with a security guard and a travel agent near the entrance. Both were killed.
The gunman is reported to have removed his overcoat before fleeing during the chaos.
Turkish media reports quote police sources as saying he may have been from Uzbekistan or Kyrgyzstan.
A manhunt is under way, Interior Minister Suleyman Soylu confirmed. “We hope the attacker will be captured soon.”
President Recep Tayyip Erdogan accused groups such as ISIS of trying “to create chaos”.
“They are trying to… demoralise our people and destabilise our country,” he added.
Turkey suffered a bloody 2016 with a series of attacks, some carried out by Kurdish militants.
But a day before the IS claim, the banned Kurdistan Workers’ Party (PKK) was quick to distance itself from the nightclub attack, saying it would “never target innocent civilians”.
Twenty-seven of those killed were foreign, according to local media, among them citizens from Israel, Russia, France, Tunisia, Lebanon, India, Belgium, Jordan and Saudi Arabia.
Victims by nationality:
Saudi Arabia: 7
Jordan, India, Morocco: two nationals from each country
Syria, Israel, France, Tunisia, Belgium, Kuwait, Canada, Russia: one national from each country
The body of one of those killed has yet to be identified.
Security guard Fatih Cakmak was among the first to die.
His brother said he narrowly escaped a double bombing three weeks ago, having been on duty when Kurdish militants launched an attack near a football stadium, killing at least 44 people, mostly police.
At least 69 people are being treated in hospital, officials said, with three in a serious condition.