Islamic State claims responsibility for Istanbul attack

Reina, quite close to the Bosporus Strait, is popular with celebrities, artists, football stars and tourists. As to the shooter, Agar described him as a "very very cold-blooded" terrorist more adept at close attacks than those trained in the military.

"The ammunition he used is also very qualified. He definitely is not someone ordinary," Agar said, noting "he used steel core bullets which can be rarely found and used. One bullet can killed more than one person at once. It is not easily obtained."

He cited the IS group as a possible mastermind behind the mass shootings, which targeted civilians in past attacks.

In his view, the deadly attack was carried out to derange the balance in Turkey, spoil the country's ongoing struggle against terror organizations outside of its territory, disturb the society's fragility even further, or have Turkey pay a price for its increasing cooperation with Russia.

"The target and the timing which coincided with New Year celebrations is very important. The attack's symbolic meaning is very important," the analyst said.

A nationwide cease-fire brokered by Turkey and Russia has been holding in Syria despite some clashes, since it was activated at midnight Friday, a monitor group reported on Saturday.

Turkey, for its part, has launched a military offensive in northern Syria since August, with a view to clearing the IS militants from the border area and preventing the Syrian Kurds from claiming more land for an autonomous region or an independent state.

In the wake of the nightclub attack, the Turkish armed forces voiced determination to press ahead with the counterterrorism efforts, which Agar described as something "quite important."