The analysis by IHS Jane's Terrorism and Insurgency Centre (JTIC) also found that just 14 percent of the strikes were against the Islamic State group.

It found that the Syrian state had increased the area under its control from 16 percent of the country in September 2015 to 47 percent in March 2018.

Russian intervention not only ensured the survival of Syrian President Bashar al-Assad's regime, it changed the course of the war.

"Russian intervention has provided the Syrian government with the space and time to concentrate forces at key strategic areas and use overwhelming force to recapture opposition-held territory," said Matthew Henman, head of JTIC at IHS Markit.

"JTIC's recorded data underlines the key role airstrikes have played in this strategy, with opposition forces largely unable to defend against, let alone replicate, the threat posed by airpower."

IHS Jane's said Assad's forces have successfully recaptured large urban centres such as Aleppo and Homs, as well as securing the border with Lebanon and containing the threat from Islamist rebels in Idlib.

Between September 2015 and March 2018, the number of Russian and Syrian strikes rose to 6,833 from 2,735.

Of these strikes, 960 were targeted the Islamic State group -- around 14 percent -- but the majority were against other rebel groups, the report found.

The strikes were "particularly concentrated in areas where the Islamic State had little or no operational presence," it said.

fb/dt/ach

IHS Global Insight

MARKIT