A U.S. official said Washington believed it was of Russian origin, but added the information was still preliminary and declined to give any more details.
Meanwhile, the Russian Defense Ministry said all of its planes in Syria had safely returned to base and that all its drones were operating "as planned."
As reported earlier, the Ministry of Foreign Affairs of Turkey accused Russia of violating country's airspace, saying two Turkish fighter F-16S were sent to intercept the Russian aircraft. Ankara handed a note of protest to the Russian ambassador in Turkey. The Russian Defense Ministry acknowledged an error by pilots, explaining it by bad weather conditions.
NATO Secretary General Jens Stoltenberg urged Russia to respect the airspace of the alliance member states and to avoid any escalation of tensions.
Later on, the Turkish Foreign Ministry said that Russia violated the airspace of Turkey not only on Oct. 3 but on the next day as well. NATO assumed that the violation was not a mere accident.
Turkish President Recep Tayyip Erdogan threatened Russia to terminate friendly relations between the two countries due to the situation around Syria. The Turkish leader emphasized that Ankara would not allow getting away with violation of its airspace, noting that "an attack on Turkey is equivalent to an attack on NATO."