According to an IHS report published on Sunday, Daesh has lost territory in Syria and Iraq which is equivalent to the size of Ireland in the last 18 months. The report added that this means the militant group is likely to further step up attacks on civilians in coming months.
The area controlled by the ultra-hardline Sunni group was reduced from 90,800 sq km in January 2015, six months after it declared a caliphate in Syria and Iraq, to 68,300 sq km, the research firm said.
The recapture of Falluja by Iraqi forces last month, a Daesh stronghold located west of Baghdad, has seen militants intensify bombings targeting Shia Muslims.
A suicide bombing left nearly 300 people dead in a busy shopping district in Baghdad a week ago. The attack was one of the group's worst attacks to date.
Daesh also lost the city of Ramadi at the end of 2015, considered a key stronghold for the group. The Iraqi military is preparing to recapture Mosul, Daesh's de facto capital.
In Syria, the Daesh group lost territory to Iranian and Russian-backed forces supporting the regime of Bashar al-Assad, and to Syria Democratic Forces (SDF) alliance who are backed by the US.
The SDF took the town of al-Shadadi in February, considered a major logistics hub for the militants. In March, Syrian and allied forces supported by Russian air strikes forced Daesh militants to withdraw from the ancient Syrian city of Palmyra and its surrounding areas.
The SDF is currently advancing to recapture areas north of Raqqa, Daesh's de facto capital in Syria.
