Nato's secretary-general has apologised to Turkey over military exercises in Norway during which Turkey's founding leader, Mustafa Kemal Ataturk, and the current president, Recep Tayyip Erdogan, were reportedly depicted as "enemies".
Mr Erdogan said Turkey withdrew 40 of its soldiers participating in the drills at Nato's Joint Warfare Centre in Stavanger, Norway, in protest at the incident and criticised the alliance.
"There can be no such unity, no such alliance," he said in an address to his ruling party's provincial leaders.
Details of the incident were sketchy but Mr Erdogan said Mr Ataturk's picture and his own name were featured on an "enemy chart" during the drills.
The individual who posted the material was described as a Norwegian civil contractor seconded by Norway, and not a Nato employee.
Nato Secretary-General Jens Stoltenberg issued a statement saying: "I apologise for the offense caused."
He said the incident was the result of an "individual's actions" and did not reflect the views of the alliance.
He added that the individual was removed from the exercise and an investigation was under way.
"It will be for the Norwegian authorities to decide on any disciplinary action," Mr Stoltenberg added. "Turkey is a valued Nato ally, which makes important contributions to allied security."
Mr Stoltenberg apologised again at the Halifax International Security Forum in Canada. He said he has already spoken with the Turkish defence chief and that it "won't create any lasting problems, and I think it's already behind us".
Norwegian defence minister Frank Bakke-Jensen apologised for the incident as well.
"The message does not reflect Norway's views or policies and I apologise for the content of the message," Mr Bakke-Jensen said. "Turkey is an important ally in Nato, and we value our good cooperation."