The Russian military says it has beefed up its air group in Syria with state-of-the art fighter jets.

Russian Defense Ministry spokesman Igor Konashenkov says Su-35 fighters have been deployed to Hemeimeem air base in Syria. Konashenkov on Monday didn't say how many Su-35s had been sent to Syria, but Russian media reported that there were four.

Russian warplanes have flown about 6,000 missions in four months.

Konashenkov said all Russian strike aircraft are being accompanied by Russian or Syrian fighter jets.

Russia added fighter escorts after a Turkish fighter jet downed a Russian bomber at the border with Syria on Nov. 24. Russia has vowed to fend off any future threats to its warplanes with fighters and long-range air defense missiles at Hemeimeem.