Russia has sent anti-aircraft missile systems to Syria to back up its air campaign, the commander of the air force Viktor Bondarev said in an interview published Thursday.

"We sent there not just fighter planes, strike aircraft and helicopters but also anti-aircraft rocket systems," Bondarev told the Komsomolskaya Pravda tabloid.

He said that Russia made the decision to bring missile systems to Syria because "we took into account every possible threat."

"There could be various force majeure situations. Let's imagine a military plane is hijacked and taken to a neighbouring country and air strikes are aimed at us. And we have to be ready for this."

A source told Interfax news agency that the systems deployed to Syria included the BUK and Pantsir systems.

"The system is set up along the lines of Israel's Iron dome," the source said.

Bondarev said Russia has "more than 50 planes and helicopters" in Syria, "precisely the number we need. At the moment, we do not need more."

He said that a Russian jet that strayed into Turkish territory in October had done so because as it flew along the Turkish border in dense cloud "the equipment showed that some ground-based air defence systems were trying to capture the plane.

"Therefore the pilot had to make an anti-missile manoeuvre. So he passed into the Turkish air a tiny bit. As we honestly admitted," Bondarev said.

The defence ministry previously said only that the plane strayed into Turkish air space on October 3 because of bad weather conditions.

Turkey said the Russian aircraft exited its airspace after it was intercepted by two Turkish F-16 fighter jets.

NATO called the incident a "serious violation".