Police in Turkey's most populous city on Sunday arrested 20 people, including 15 foreign nationals, over links to ISIL, state-run Anadolu Agency reported.
The suspects, who were linked to ISIL leaders in Syria and Iraq, were arrested at four addresses in three districts in Istanbul.
The police said the suspects were planning an attack during New Year's Eve celebrations in the city.
More than 300 people have lost their lives in ISIL-claimed attacks in Turkey. On New Year's Eve in 2016, 39 people were killed and scores of others were wounded, including Turkish and foreign nationals, in an attack in a nightclub in Istanbul.
A Turkish special forces police officer guards the entrance of the Presidential Palace in Ankara, Turkey. /Reuters Photo
A Turkish special forces police officer guards the entrance of the Presidential Palace in Ankara, Turkey. /Reuters Photo
Ahead of the attack anniversary, Turkey has tightened security across the country.
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.
The authorities also banned New Year celebrations in some of the most popular areas and all road access to these areas will be cut off from the afternoon.
In the capital Ankara, similar measures have been taking with 9,700 police deployed and New Year celebrations banned in the central Kizilay Square.