Baghdad: Islamic State (IS) has lost more than a quarter of the territory it once controlled, BBC reported showing new data.
Security and defence analysts IHS say the group's control has shrunk by 28 per cent since its height in January 2015.
In the first nine months of this year, IS' territory fell from 78,000sqkm to 65,500sqkm – an area equivalent to the size of Sri Lanka – IHS analysts said.
However, IS losses have slowed in the three months to October.
The slowdown appears to coincide with Russia reducing the number of air strikes against IS targets, IHS has observed.
At the start of the year, some 26pc targeted IS, but by the summer it had dropped to just 17pc.
"Last September, President Putin said it was Russia's mission to fight international terrorism and specifically the Islamic State," said Alex Kokcharov, principal Russia analyst at IHS. "Our data suggests that is not the case.
"Russia's priority is to provide military support to the Assad government and, most likely, transform the Syrian civil war from a multi-party conflict into a binary one between the Syrian government and jihadist groups like the Islamic State; thereby undermining the case for providing international support to the opposition."
Yet the losses the group has sustained are still significant, experts say. IS has been pushed back 10km from the Turkish border, while Iraqi forces have secured Qayyarah Airbase, a key strategic facility 60km south of the IS stronghold of Mosul.