RUSSIA has sent missile systems to Syria to protect its military forces in the war-torn country as it continues to blitz the Islamic State.

Colonel General Viktor Bondarev, head of Russia's air force, warned fighter jets could be hijacked in neighbouring countries and used to attack Russian forces.

"We have sent not only fighter jets, bombers and helicopters, but also missile systems. We must be ready."

The Colonel warning comes after reports that the number of Russian military forces in Syria has swelled to 4,000.

Moscow began air strikes against ISIS at the end of September and has reportedly killed hundreds of fanatics.

Bondarev also revealed a Russian pilot was forced to violate Turkish airspace last month to avoid a missile defence system on the ground.

He said: "Our plane was completing a strike task in northern Syria. There was heavy cloud cover. 

"When our fighter started flying along the border with Turkey, the system showed that some sort of anti-missile defence systems were attempting to lock onto the warplan.

"So the pilot was forced to make an anti-missile manoeuvre in just seconds, and entered Turkish airspace a bit, which we honestly admitted to."

Russia's intervention in the Syria crisis has been widely slammed by US officials since the air strikes began. 

They have claimed Vladimir Putin is only interested in propping up Syrian dictator Bashar al-Asssad – allegations which the Russian president denies.

Last month he said: "I think some of our partners simply have mush for brains.