BEIRUT // ISIL has lost a quarter of its territory – or an area the size of Ireland – to hostile forces during the past 18 months in Iraq and Syria and will probably increase attacks on civilians in coming months, experts say.

The territory controlled by the extremist group shrank from 90,800 sq km in January last year, six months after it declared a caliphate in Syria and Iraq, to 68,300 sq km, global research company IHS said in a report.

“As the ISIL’s caliphate shrinks and it becomes increasingly clear its governance project is failing, the group is re-prioritising insurgency,” said Columb Strack, senior analyst at IHS and lead analyst for the IHS conflict monitor. “As a result, we expect an increase in mass casualty attacks and sabotage of economic infrastructure across Iraq and Syria, and further afield, including Europe.”

The Iraqi military’s recapture last month of Fallujah, an ISIL stronghold just west of Baghdad, led the insurgents to increase bombings on Shiite targets.

About 300 people died when an ISIL suicide bomber struck in a busy shopping district in Baghdad a week ago, in one of the worst such attacks by the group to date.

ISIL lost control of the city of Ramadi at the end of last year, another key stronghold for the group, which captured large ­areas of Iraq in 2014. The army is now gearing up to retake Mosul, the largest city in Iraq’s north and ISIL’s de facto capital.

In Syria, ISIL lost ground this year to Russian and Iranian-backed forces supporting president Bashar Al Assad and to the US-backed Syria Democratic Forces (SDF) alliance.

In February the SDF captured the town of Al Shadadi, a major logistics centre for the militants, and in March Syrian and allied forces backed by Russian air raids drove ISIL out of the ancient Syrian city of Palmyra and surrounding areas.

An SDF advance is on to retake areas north of ISIL’s de facto capital in Syria, Raqqa.

Meanwhile, fighting between Syrian rebels and Mr Al Assad’s forces raged on Sunday. Regime troops repelled a fierce assault by opposition fighters seeking to reopen their only supply route into Aleppo city, killing at least 29 rebels, the Syrian Observatory for Human Rights said.

The offensive sought to push regime forces back from the Castello Road that leads into the opposition-held eastern half of Aleppo city, which is now besieged by government troops.

Castello Road was effectively severed by government forces on Thursday when they seized a hilltop within firing range of the key supply line.

The Observatory said at least four civilians had been also killed in regime air raids overnight on the rebel-held town of Douma, east of Damascus.

* Reuters and Agence France-Presse