Leanne Nasser was a bright-eyed Arab Israeli teenager, in Istanbul with friends for New Year’s despite her father’s concerns about safety. Fatih Cakmak, who survived a bomb attack only weeks ago, was hired to work security for a popular nightclub.

Both were among those who died early Sunday when a gunman, brandishing an assault rifle, stormed Istanbul’s famed Reina club on the banks of the Bosporus, gunning down unsuspecting New Year’s revelers in a rampage that was one of the city’s worst mass killings in recent memory.

The assailant remained at large Sunday night and unidentified except for blurred glimpses of him in security camera footage that showed gunshots sparking off the pavement and victims crumpling to the ground. Thirty-nine people were killed, many of them foreigners, 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.

Among the victims of Sunday’s attack, in Istanbul’s Ortakoy district, were an Iraqi student, a Turkish police officer and two Lebanese fitness trainers. Authorities were working Sunday to identify the dead; citizens of at least eight countries, including Turkey, were killed in the assault.

“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 in Istanbul where he studied, Kemburgaz University, announced his death on Twitter.

(Haberturk Gazetesi Yildirim)

Hassan Alaa, who was close to Jalal, struggled with the news of his boyhood friend’s death. Jalal, an only child, was active and 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 Irbil. “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 a nightclub in Orlando in 2016. And like those attacks — with a disproportionate tally of young victims, all of whom had been enjoying a night out — the carnage on the Bosporus left a city reeling from a sense of shock and grief.

In Paris and Orlando, assault rifles were used to target largely cosmopolitan and international crowds. The Islamic State claimed responsibility for those attacks. The extremist group has carried out attacks in Turkey in recent years, but there was no claim of responsibility for the massacre early Sunday.

It began just after 1 a.m., when the assailant shot dead a 22-year-old police officer, Burak Yildiz, and a chauffeur 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, 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.”

Mustafa Sezgin Seymen, 32, was at Reina with his fiancee, Sezen Arseven. She was wounded; Seymen, a native of the Black Sea city of Trabzon, was killed.

“I’m returning without you from the place we went together,” Arseven wrote of Seymen in a public Facebook post on Sunday.

“I have lost my spouse, my life partner, my most beloved,” she wrote.

Officials on Sunday called the nightclub attack a “massacre” and an act of terrorism. Turkish 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.

It was the fourth major attack in Turkey in less than a month, including the high-profile assassination of the Russian ambassador by a Turkish policeman and a car bomb assault against riot police at a soccer stadium in Istanbul. The stadium attack, which killed 44 police officers, was claimed by separatist Kurdish militants, who have waged a decades-long insurgency against the Turkish state.

The attacks have posed a severe challenge to Erdogan’s government, which has appeared to lurch from crisis to crisis since the authorities put down an attempted coup in July. The state’s resources have been stretched thin as it tries to respond to the cascading calamities. After the coup, the government launched a crackdown on its perceived enemies, arresting thousands of people. At the same time, Turkey has deepened its involvement in the Syrian war while escalating its confrontation with Kurdish groups.

Cakmak, the security guard, was working at the stadium when the car bomb detonated on Dec. 11, Turkish media reported.

“They killed my brother. He died for nothing,” Erhan Cakmak said outside the central morgue Sunday in Istanbul, in a video circulated by the private Dogan News Agency.

Fatih Cakmak’s Facebook profile photo shows him with the renowned French soccer player and Real Madrid manager ­Zinedine Zidane.

Relatives and friends of one of the Lebanese victims, Haykal Moussalem, a 35-year-old fitness trainer, arrived at the morgue Sunday saying they had not been able to locate him.

Lebanon’s consul general in Istanbul later confirmed that Moussalem had been killed, along with at least two other young Lebanese citizens, Elias Wardini and Rita Chami, according to a statement on the site of the country’s national news agency.

Pictures on social media showed Moussalem, newly married, on a trip to Italy with his wife, and supervising training sessions in a gym. Another picture that circulated showed Wardini and Chami smiling in the sleet on an Istanbul street.

In Israel, Nasser’s father, speaking to local media, said he implored his 19-year-old daughter not to travel to Istanbul because of recent attacks. Israel’s Foreign Ministry said one of her friends, 18-year-old Ruaa Mansour, was among those injured.

Late Sunday, the French Foreign Ministry said a Franco-Tunisian woman and her Tunisian husband had been killed. The Jordanian Foreign Ministry said three of its nationals were also confirmed dead.

According to Turkey’s state-run news agency, Anadolu, nearly two-thirds of the victims were foreigners.

The U.S. State Department on Sunday warned U.S. citizens in Istanbul to limit movements “to an absolute minimum” while the search for the assailant continues.

Jalal, the Iraqi student, “was one of the kindest people I knew. He would never hold a grudge,” his friend Alaa said.

“He loved his life [in Istanbul],” Alaa said. “He enjoyed everything in it and wanted to stay for good.”

Fahim reported from Cairo. Heba Habib in Stockholm contributed

to this report.

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