ISTANBUL — The gunman responsible for the massacre at an Istanbul nightclub remained at large Sunday night, and unidentified except for blurred glimpses of him in surveillance footage that showed gunshots and victims crumpling to the ground.
Thirty-nine people were killed in the latest in a string of assaults that have roiled Turkey as it battles insurgents at home and across the border in war-torn Syria. At least 70 people were wounded.
Nearly two-thirds of the people killed were foreigners, most from the Middle East, Turkey’s state-run Anadolu Agency said. India and Belgium also reported that their citizens were among the casualties. Anadolu said the bodies of 25 foreign nationals killed in the attack would be delivered to their families Monday.
A US State Department official who spoke on condition of anonymity said one American man was among those wounded, the Associated Press reported. Turkey’s minister for family and social policies, Fatma Betul Sayan Kaya, said citizens of Saudi Arabia, Morocco, Lebanon, and Libya were among those injured.
There was no claim of responsibility for the attack in the Reina Club on the banks of the Bosporus, which began about 1:45 a.m. Sunday. An estimated 600 people were celebrating inside when the rampage began.
NTV, a private news channel, said the assailant was wearing a Santa Claus outfit when he entered the club, but Prime Minister Binali Yildirim later denied that report. Yildirim said the attacker left a gun at the club and escaped by ‘‘taking advantage of the chaos’’ that ensued.
Among those killed was Leanne Nasse, an Arab-Israeli teenager who was in Istanbul with friends for the New Year, despite her father’s concerns about safety. Fatih Cakmak, who survived a bomb attack only weeks ago, was hired to work security for the popular club.
Among the other victims of the attack, in Istanbul’s Ortakoy district, were an Iraqi student, a Turkish police officer, and two Lebanese fitness trainers. Authorities still were working Sunday to identify all the dead.
‘‘Please answer my comment, and tell me you have not died,’’ one Facebook user, Sheery Rudan, posted on the profile photo of 22-year-old Mustafa Jalal, an Iraqi student from Kirkuk. The school where he studied, Kemburgaz University, announced his death on Twitter.
Hassan Alaa, who was close to Jalal, struggled with the news of his boyhood friend’s death. Jalal, who was an only child, was active, outgoing, and loved cars and swimming, he said.
‘‘I can’t believe this. We would have breakfast together every day,’’ Alaa said, when reached in the Iraqi city of Erbil. ‘‘And now he’s gone. Before he left for the club, he wished me a happy birthday and we were joking around.’’
The assault, which targeted a posh, sprawling venue popular with Istanbul’s elite, recalled similar attacks on a concert hall in Paris in 2015 and nightclub in Orlando in 2016.
And like the previous attacks — with their disproportianate tally of young victims, all of whom had been enjoying a night out — the carnage on the Bosporus left Istanbul reeling from a similar sense of shock and grief.
In Paris and Orlando, one or more gunmen used assault rifles to target largely cosmopolitan and international crowds. The Islamic State claimed responsibility for those attacks. The jihadist group has carried out attacks in Turkey in recent years.
Sunday’s attack began when the assailant shot and killed a 22-year-old police officer, Burak Yildiz, and a chaffeur for a tourism company, Ayhan Arik, on the street outside the club, according to Turkish media reports. The sound of gunshots sent panicked patrons scrambling for cover at the waterside as the gunman came inside, witnesses said.
One patron, professional soccer player Sefa Boydas, described on Twitter the chaos at the club. In a series of posts that were later deleted, Boydas said he did not see who was shooting, but he noted that police arrived on the scene quickly. He carried his girlfriend, who was wearing high heels, he said, out of the club to safety.
‘‘At first we thought some men were fighting with each other,’’ a Lebanese woman who gave her name as Hadeel told the Reuters news agency. She was in the club with her husband and a friend.
‘‘We heard the guy screaming Allahu Akbar,’’ she said, which is Arabic for ‘‘God is great.’’
‘‘We heard his footsteps crushing the broken glass,’’ she said. ‘‘We got out through the kitchen, there was blood everywhere and bodies.’’
Turkish officials called the attack terrorism. President Recep Tayyip Erdogan said it was meant to ‘‘trigger chaos.’’ We ‘‘will never give passage to these dirty games,’’ Erdogan said in a statement posted on the presidential website.
Sunday’s attack was the fourth major one in Turkey in less than a month, including the assassination of the Russian ambassador by a Turkish policeman, and a brazen car bomb assault against riot police at a soccer stadium in Istanbul. That attack, which killed 44 police, was claimed by separatist Kurdish militants, who have waged a decades-long insurgency against the Turkish state.
