Erdogan announced on Friday that his country has withdrawn from the Trident Javelin war games, as he protested at another incident in which modern Turkey's founder, Mustafa Kemal Ataturk, was shown as "hostile".
NATO's secretary general has apologised to Turkey after a civilian contractor depicted President Recep Tayyip Erdogan as an "enemy collaborator" during a military exercise in Norway.
The president said he was informed about the issue by Chief of General Staff Gen. Hulusi Akar and EU Affairs Minister Omer Celik.
Turkey withdrew its 40 soldiers from the exercise after the incident, it added. "I told them not to waste a single minute", he said before criticizing the alliance and the allies.
"It's not possible to have this kind of alliance", he added.
Some Turkish media speculated that his comments indicated that images of Ataturk and Erdogan had been used for target practice in the exercise.
He said the messages had been sent on the private computer network used in the drill, "and in no way" reflected Norway's views.
Under Erdogan, Turkey's relations with NATO's leadership and the European Union have frayed in recent years.
Western allies have been particularly troubled by a deal for Ankara to purchase an S-400 air defence system from Russian Federation. "The incidents were the result of an individual's actions and do not reflect the views of North Atlantic Treaty Organisation". The statement said: "I apologize for the offense that has been caused".
Following Erdogan's remarks, North Atlantic Treaty Organisation clarified that two separate incidents occurred.
Stoltenberg's statement said that the individual in question "was immediately removed from the exercise by the Joint Warfare Centre, and an investigation is underway".
The country has the second largest military force in North Atlantic Treaty Organisation, and is involved both in coalition efforts against so-called Islamic State and in Nato's Afghanistan mission.