The arrests were carried out during an operation by teams from the Istanbul Police’s counter-terrorism unit and the National Intelligence Organization (MIT) in five provinces, including Istanbul, Vasip Sahin told reporters on Thursday.

Sahin also said the operations were conducted following intelligence that the terrorists were preparing for a "sensational" attack in Istanbul.

"One of these 44 suspects was the organizer of the Besiktas stadium attack who explored the area and then jumped out of the bomb-laden car at the last moment,” he said, referring to a December 2016 attack after a football match at Vodafone Stadium which killed 46 people and injured 243.

“The other is the organizer of the bomb attack in Vezneciler targeting the riot police service bus,” a June attack that killed 11, including seven police officers, and wounded 36 people, he added.

The PKK -- listed as a terrorist organization by Turkey, the U.S. and the EU -- resumed its armed campaign against Turkey in July 2015.

Since then, it has been responsible for the deaths of some 1,200 Turkish security personnel and civilians, including many women and children.

Anadolu Agency