The Islamic State group on Monday claimed the shooting rampage inside a glamorous Istanbul nightclub on New Year's night that killed 39 people, as police hunted the attacker who remains on the run.
With foreigners making up the majority of those killed in Sunday's attack, families were due to reclaim the bodies of more than two dozen non-Turkish and mainly Arab victims.
The shooting, which unleashed scenes of carnage and panic among party-goers at one of Istanbul's swankiest venues, took place just 75 minutes into 2017 after a bloody year in Turkey in which hundreds of people were killed in violence blamed on both IS jihadists and Kurdish militants.
In a statement circulated on social media, the jihadist group said one of the "soldiers of the caliphate" had carried out the attack on the Reina nightclub.
It accused Turkey, a majority-Muslim country, of being a servant of Christians, in a possible reference to Ankara's alliance with the international coalition fighting IS in neighbouring Syria and Iraq.
The statement said the assault was in response to Turkey's military intervention against IS in war-ravaged Syria.
Turkish troops are pressing on with a four-month incursion in Syria to oust IS jihadists and Kurdish militants from the border area.
In the last few weeks, the forces have encountered fierce opposition from the jihadists around the town of Al-Bab. The army said Turkish war planes launched new air strikes around Al Bab.
- 'Danger continues' -
Arriving by taxi at the plush Reina nightclub on the shores of the Bosphorus, the gunman produced a weapon, reportedly a Kalashnikov, and shot dead a policeman and civilian at the entrance.
According to the Hurriyet daily, the gunman then fired off four magazines containing a total of 120 bullets around the club, as terrified guests flung themselves into the freezing waters of the Bosphorus in panic.
But after changing clothes, the gunman left the nightclub in the ensuing chaos and has managed to evade security forces.
Interior Minister Suleyman Soylu said Sunday that intense efforts were under way to find the gunman, and expressed hope that he would be captured soon.
Late on Sunday, police rushed to Istanbul's Kurucesme district after a tip-off but the operation did not produce any arrest.
"The danger continues," wrote columnist Abdulkadir Selvi in Hurriyet.
"So long as this terrorist is not seized we do not know when and where a massacre could take place."
Hurriyet said investigators believe the attacker may be from the Central Asian states of Kyrgyzstan or Uzbekistan.
Investigators also consider it possible that the attacker is linked to the same cell that in June carried out a triple suicide bombing and gun attack at Istanbul's Ataturk airport blamed on IS that left 47 people dead, the paper added.
Turkey also received intelligence from the United States on December 30 warning of the risk of attacks by IS in Istanbul and Ankara on New Year's night, the paper said,
President Recep Tayyip Erdogan, who said the nightclub bloodbath sought to sow "chaos", was on Monday due to chair a meeting of the Turkish cabinet.
Prime Minister Binali Yildirim meanwhile denied reports the attacker had worn a Santa Claus costume.
Soylu said the assailant had arrived with a gun concealed under an overcoat but subsequently exited the venue wearing a different garment.
- 'No crime more cynical' -
NTV television said that the bodies of 25 foreigners killed in the attack were to be handed back to their families on Monday following identification.
According to Turkish press reports, the latest figures show 11 Turks were killed in the attack alongside 27 foreigners, including one Belgian-Turkish dual national. One victim is still unidentified.
Sixty-five people were wounded.
The foreigners who died -- most of them from Arab countries -- had come to the club to celebrate a special night in style.
They included three Lebanese nationals, two Jordanians and three Iraqis, officials in their respective countries said.
A Canadian woman, a Russian woman and a teenage Arab Israeli woman were also among dead. Turkish press reports said at least seven Saudi nationals died but this has yet to be confirmed by Riyadh.
The attack evoked memories of the November 2015 carnage in Paris when IS jihadists unleashed a gun and bombing rampage on nightspots in the French capital, killing 130 people including 90 at the Bataclan concert hall.
World leaders rushed to condemn the nightclub shooting, with Russian President Vladimir Putin saying it was "hard to imagine a crime more cynical than the killing of civilians during a New Year's celebration".