The head of Russian airforce, Colonel General Viktor Bondarev, has said Russia has sent a missile system to Syria to protect their military forces there.
Colonel Bondarev said their fighter jets could be hijacked in countries neighbouring Syria and used to attack Russian forces.
"We have calculated all possible threats. We have sent not only fighter jets, bombers and helicopters, but also missile systems," Colonel General Bondarev told Komsomolskaya Pravda newspaper on Thursday, Reuters reported.
A top US State Department official meanwhile said on Wednesday that Russia has deployed its heavy artillery on near the battlefield cities of Homs and Hama.
"Now Russia is fielding its own artillery and other ground assets around Hama and Homs, greatly increasing their soldiers' vulnerability to counterattack," US State Department assistant secretary of state for European and Eurasian affairs, Victoria Nuland, said.
Missile systems are used to protect the military presence of the armies from the attacks of the fighter jets of the opponent forces. There are three sides in Syria using fighter jets which are the Assad regime, US-led coalition forces and Russia.
London-based Syrian Observatory for Human Rights (SOHR) provides information from an extensive network of Syrian activists in which they said on October 2014, that defected Iraqi military officers were teaching DAESH terrorists how to fly three commandeered fighter jets in Syria.
Despite the claims of flying fighter jets by DAESH militants, there is no record that DAESH terrorists used fighter jets they have captured from Assad forces to use against their opponents.