Presidential spokesman İbrahim Kalın said Monday an incident during a recent NATO drill where the names of Turkish Republic founder Mustafa Kemal Atatürk and current President Recep Tayyip Erdoğan were used in an "enemy chart" should be investigated carefully.

Speaking to France 24, Kalın said Turkey's participation in NATO dates back more than 50 years, adding, "This is one incident, but of course we are a strong ally in NATO and have participated in many exercises," referring to the drill incident in Norway which led to Turkey withdrawing its troops.

Turkey withdrew its troops from NATO's Trident Javelin 2017 (TRJN17) exercise in Norway on Friday after a civilian Norwegian official depicted President Erdoğan as an "enemy collaborator."

A portrait of Turkey's founder, Mustafa Kemal Atatürk, was also shown in the "hostile leader list" during a computer-assisted exercise of the drill.

"Obviously, it's completely unacceptable to do this to any country, especially in relation to our founding President Atatürk and current president, and expect Turkey not to react to it. That's not possible," Kalın said.

"Of course, this incident has to be studied and investigated very, very carefully – who did it, who put those pictures in there, etc.," he further indicated.

He added that Turkey received an apology, which is fine, but one has to explain how within a system like NATO – a military alliance with such a strict disciplinary statute – such a thing can happen.

Responding to a question on whether it was an accident or not, Kalın said: "Well, I don't know the details. We will see. We've relied on NATO's explanations so far, and I think there will be an investigation. We have heard that a couple of people were fired but want to know how this could happen in NATO so it won't happen again."

Kalın also said Turkey is not considering severing ties with NATO.

Meanwhile, British ambassador to Ankara Richard Moore said the NATO drill scandal is an embarrassing incident.

"I understand the sensitivity of the issue for Turkey, but this is not a matter that was done by NATO, it is the fault of one or two people," Moore said during a meeting with the press due to the termination of his tenure. He also said NATO apologized quite quickly for the incident and that it is absurd to say that Turkey is moving away from NATO.

Speaking on the issue, Bulgaria's prime minister praised on Monday Turkey's decision to withdraw from the NATO drill following the incidents, stressing that Turkey must remain a strategic partner for the bloc and the EU.

President Erdoğan's message on withdrawing Turkey's 40 soldiers "is also a message I have been giving at the European Council for long time," Boyko Borisov told a university in capital Sofia.

"Because there is a contradiction in interpreting events and because European leaders are totally rejecting them when President Erdoğan and Turkey are the topics," he added.

Deputy Prime Minister Bekir Bozdağ also said on Monday that, though Turkey accepted NATO's apology, the scandal in Norway should not be covered up, and the military alliance should investigate its chief officers involved in the incident.

"The NATO drill scandal in Norway not only targeted the founder of the Turkish Republic, Mustafa Kemal Atatürk, but also President Recep Tayyip Erdoğan. It disrespected the whole nation," Bozdağ said, adding that it is one of the biggest scandals in NATO's history.

Turkey's EU Affairs Minister Ömer Çelik also called for an investigation on Sunday of the NATO chain of command involved in the drill.

Çelik also expressed that the incident was similar to the methods used by the Gülenist Terror Group (FETÖ), which orchestrated a deadly coup attempt in Turkey last year as part of a long-running attempt to overthrow the Turkish government.

"They [FETÖ] are using all of their assets to harm Turkey in order to create negative developments in the country. This was very similar to methods they use," he said.

FETÖ, led-by its U.S.-based fugitive leader Fetullah Gülen, masterminded the July 15 defeated coup that killed 250 civilians and left around 2,000 others injured.