With debates surrounding an intercepted Syrian plane in full swing, Erdoğan said on Thursday that the plane was forced to land because a civilian plane cannot carry materials used in the defense industry.
Speaking during a joint press conference with Kazakh President Nursultan Nazarbayev in Ankara, Erdoğan said carrying non-civilian materials is against civil aviation rules and this is why the plane was not allowed to pass through Turkey's airspace.
A Syrian Air Airbus A320 en route from Moscow was intercepted by F16 jets as it entered Turkish airspace and escorted to the capital's Esenboğa Airport on Wednesday. The station said authorities grounded the plane on suspicion that it was carrying heavy weapons.
He noted that passengers were held at the airport for nine hours and the plane resumed its journey when the investigation was finished.
Erdoğan declined to give the source of the intelligence obtained by Turkey on the presence of non-civilian cargo on the plane. He said a report that includes details on the seized material and the intended recipient of the cargo is being prepared by officials.
However, he did reveal that the Syrian Defense Ministry appears to be the buyer of the confiscated materials, according to documents found on the plane.
"This was munitions from the Russian equivalent of our Mechanical and Chemical Industry Corporation being sent to the Syrian Defence Ministry," Erdoğan told reporters, referring to a state-run Turkish manufacturer that supplies the country's army.
The United States said it backed Turkey's decision to intercept the plane.
"Any transfer of any military equipment to the Syrian regime at this time is very concerning, and we look forward to hearing more from the Turkish side when they get to the bottom of what they found," said US State Department spokeswoman Victoria Nuland.
She declined to comment on Turkish reports that the intelligence on the plane's cargo had come from the United States.
Russia's foreign ministry declined immediate comment but its arms export agency said earlier it had no cargo on the flight, while the Interfax news agency quoted Yelena Kara-Sal, a top Russian consular official, as saying the cargo seized by the Turkish authorities was not of Russian origin.
The Moscow airport that cleared the Syrian plane for takeoff denied there was any forbidden cargo on board.
"No objects whose transportation would have been forbidden under aviation regulations were on board," said Vnukovo Airport spokeswoman Yelena Krylova, ITAR-Tass reported.
Krylova said all documentation related to the cargo was in order. She would not say who had sent the cargo.
Syrian Air chief Ghaida Abdulatif told reporters in Damascus the plane was carrying civilian electrical equipment.
In the meantime, Turkey's Foreign Ministry issued a statement saying that the pilot of the Syrian Air plane from Moscow had been warned of Turkey's intention to ground it as he approached from the Black Sea on Wednesday evening. It said he was given the chance to turn back, but that he decided to continue his course.
Rejecting claims that passengers were ill-treated, the Turkish statement said they were allowed to leave the plane if they wanted and that there was a medical crew and ambulances on standby. It also said that the pilot did not provide a passenger list and therefore Turkish officials did not know there were Russians on board until after it landed.
The statement came as a response to the statements of Russian Foreign Ministry spokesman Alexander Lukashevich who said earlier Thursday that Russia was concerned that "the lives and safety of the passengers, among whom were 17 Russian citizens, had been endangered."
He said Turkey without explanation denied Russian consular officials and a doctor access to the passengers, who had not been allowed into the airport for eight hours or provided with food.
During his address to journalists, Erdoğan also dismissed suggestions that Russian President Vladimir Putin delayed an upcoming visit to Turkey due to a conflict over the incident.
Erdoğan said he and Putin held a phone conversation four days ago and the date of the visit was finally determined by officials from the Turkish Foreign Ministry and their Russian counterparts.