IS has lost more than a quarter of the territory it once controlled in Iraq and Syria, new data shows.

Analysis by defence analysts IHS shows that the area under the terror group's control has shrunk by 28 percent since its peak in January 2015 as counter insurgents and air strikes push the jihadists back.

In the first nine months of this year, IS lost a chunk of territory roughly the size of Sri Lanka as the total area under its control fell from 30,115 sq miles to 25,290 sq miles.

But the rate of territory loss appears to have slowed as Russia begins scaling back the number of air strikes against IS targets.