Turkey on Sunday arrested more suspected IS jihadists in a major crackdown on the extremist group ahead of a New Year overshadowed by the first anniversary of the nightclub terror attack that left 39 dead.
Just minutes into 2017, Istanbul was rocked by an attack by an Uzbek gunman acting on behalf of IS who fired indiscriminately on the mainly foreign revellers at the Reina club on the Bosphorus.
It was another body blow to Turkey under President Recep Tayyip Erdogan after a year of attacks by jihadists and Kurdish rebels as well as a failed coup.
However there has been no major attack in Turkey in 2017 since the Reina murders, and security forces this year appear to be taking every possible precaution to ensure this New Year passes without incident.
In pre-dawn raids Sunday, authorities detained 20 suspected IS members in Istanbul, 15 of them foreigners, who are believed to have spent time in Syria or Iraq, the Dogan news agency said.
Five more -- three Syrians, an Iraqi and a Russian Chechen -- were detained in Ankara, state-run Anadolu said.
Turkish media have said the authorities had already detained some 200 suspected jihadists in recent days -- including 75 in Istanbul and Ankara on Friday -- fearing they could launch an attack over the New Year.
According to some reports, the government is particularly anxious IS fighters who left the Syrian city of Raqa after its capture by pro-Kurdish militia this year have flooded back into Turkey.
A total of 37,000 police will be deployed in Istanbul alone on New Year's night, more than double the number last year, according to Istanbul governor Vasip Sahin.
Some 4,000 members of the gendarmerie and coastguard are also being put on duty.
Meanwhile, authorities have either scrapped or banned any New Year celebrations in some of the most popular areas for revellers, including the major hub of Taksim Square, the buzzing area of Besiktas and upscale shopping district of Sisli.
Turkish state news agency Anadolu said that police disguised as lottery ticket and hot chestnut sellers would be deployed around Taksim to ensure security.
Officers also frisked passengers on the city's ferries while heavy goods vehicles are banned from accessing the city centre from Sunday morning to Monday.
"We are having very serious security measures to ensure that our citizens, God willing, see in the New Year in peace and security," Sahin said.
In the capital Ankara, similar measures have been taken with 9,700 police deployed and roads closed on the way to the central Kizilay Square.
The Reina nightclub -- once the haunt of Turkish football stars and even foreign celebrities -- never reopened after the massacre. The authorities later bulldozed it on May 22, saying its owner had violated planning regulations.
A few dozen people attended a small ceremony organised by the local authorities to remember the victims, laying wreaths at their portraits outside the former entrance to the club.
"I'm no longer myself. This should never have happened. What did my brother do wrong? It's incomprehensible," said Tarik Arik, whose travel agent brother drove clients to Reina that night and was killed in the attack.
Gunman Abdulkadir Masharipov was arrested after a 17 day manhunt hunkering down in a humdrum residential district of Istanbul, in a major triumph for the Turkish police that gave access to a potential goldmine of intelligence about IS activities.
He confessed to have taken his orders to carry out the attack from a Syria-based Russian jihadist with the codename Abu Jihad. Masharipov had first intended to attack Taksim Square but seeing the high security switched his target to the Reina club.
Masharipov and more than 50 other suspects went on trial in Istanbul on December 11. The Uzbek faces 40 life sentences for each of the victims and the crime itself.
Facing similar charges is his wife Zarina Nurullayeva, who denied any involvement in the plot. Masharipov has refused to testify in the trial, which is now due to resume on March 26.