An increasing number of forces fighting the Islamic State in the Middle East appears to be taking its toll on the terror group, which has lost around 22 percent of its territory in Iraq and Syria over the past 15 months, a new study reveals.

Despite territorial advances last summer in the region, ISIS lost 14 percent of the territory under its control in 2015 and another 8 percent in the first three months of this year alone, according to IHS Jane’s 360, a British monitoring group.

The group says ISIS has been hurt by airstrikes from a U.S.-led campaign and from Russia’s mission in Syria, as well as Syrian Kurdish factions linked with Arab allies and the Iraqi military – which is backed by Iranian-sponsored Shiite militias.

Forces loyal to Syrian President Bashar al-Assad are also approaching the central city of Palmyra, the site of an ancient heritage site that ISIS has been ransacking since last year, according to the Syrian Observatory for Human Rights.

"Isolation and further military defeats will make it harder for the Islamic State to attract new recruits to Syria from the pool of foreign jihadis," said Columb Strack, a Middle East analyst at IHS Jane’s 360.

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