Sukhoi Su-24 attack aircraft of Russia’s air group in Syria has crashed in Syrian territory, presumably, as a result of an attack from the ground, the Russian Defense Ministry has said. The Defense Ministry said the plane was at an altitude of 6,000 meters. The pilots’ fate is unclear at the moment. According to early reports, both managed to eject themselves. "A probe is in progress into the circumstances of the Russian plane’s crash. The Defense Ministry says the plane invariably stayed within Syrian airspace. Objective monitoring data confirm this," the Defense Ministry said. Earlier, some media claimed the plane that crashed in Syria had allegedly violated Turkish airspace and was shot down by Turkish Air Force planes. Russian airstrikes against the Islamic State terrorist group in Syria started on September 30. Russia intensified its airstrikes against the terrorists after it was reported that the crash of the Russian A321 plane in Egypt was caused by a terrorist bomb exploding on board. Russia has involved long-range aviation in its air strikes and has enforced the air grouping deployed in Syria. Russia's air grouping involves 69 aircraft, including Su-34 bombers, Su-24M and Su-25 attack aircraft, Su-30SM and Su-27SM3 fighters and Mi-8 and Mi-24 helicopters.