Islamic State has claimed responsibility for the New Year nightclub massacre in Istanbul as the hunt continues for the gunman.
In a statement, the militant group hailed the "heroic soldier of the caliphate" who carried out the attack at the popular Reina club, which left 39 dead and 69 wounded, four critically.
Police are said to be investigating whether the killer belonged to the same terror cell that carried out a deadly suicide bomb and gun attack at Istanbul's Ataturk airport last June.
There are also reports Turkey received an intelligence tip-off from the US about the threat of a New Year attack although it did not give details of where it could take place.
Ankara authorities have said nearly 150 people have been detained in the past week over suspected links to IS.
Twenty-five of those killed at the nightclub were reportedly foreign citizens, including an 18-year-old Israeli woman, three Indians, three Lebanese, a woman with dual French-Tunisian citizenship and her Tunisian husband, three Jordanians, a Belgian national, a Kuwaiti citizen and a Canadian.
CCTV footage has emerged of the moment the gunman opened fire outside the club before storming the building that was packed with up to 600 revellers celebrating the New Year.
He first shot dead policeman Burak Yildiz and travel agent Ayhan Arik at the front of the venue at around 1.15am local time, before entering and firing 120 bullets at party-goers.
It was initially reported the assailant, armed with a long-barrelled gun, had been wearing a Father Christmas outfit but this was later denied by the Turkish prime minister.
The attacker is believed to have changed his clothes before escaping the scene.
Interior minister Suleyman Soylu said: "This was a massacre, a truly inhuman savagery."
Witnesses described diving under tables as the assailant opened fire, while one reveller told how she had to lift dead bodies off her to escape the building after the attack.
Some party-goers jumped into the nearby Bosphorus to escape the slaughter in the Ortakoy district.
President Recep Tayyip Erdogan has said the attack was designed to destabilise the country.
The Foreign and Commonwealth Office (FCO) said UK tourists should follow the advice of local authorities while remaining vigilant.
Attempts are being made to see whether any Britons were among the dead and injured.
Prime Minister Theresa May has written to Mr Erdogan to underline the UK's commitment to defeating terrorism following the New Year attack.
The attack happened despite heightened security in major Turkish cities over New Year.
Both Ankara and Istanbul were targeted by a series of attacks in 2016 carried out by the Islamic State group or Kurdish rebels and leaving 180 people dead.