BEIRUT, June 29, 2024 (BSS/AFP) - Islamic State fighters have killed nearly 4,100 people in Syria since 2019 when the jihadists lost their last stronghold in the country, a war monitor said Saturday.

IS overran large swathes of Syria and Iraq in 2014, proclaiming a so-called caliphate and launching a reign of terror in June of that year.

In March 2019, the jihadist group lost its last scraps of Syrian territory in a Kurdish-led military campaign backed by a US-led coalition, but remnants continue to launch deadly attacks from desert hideouts.

IS fighters "have killed about 4,100 people in more than 2,550 operations in areas controlled by the regime or" the semi-autonomous Kurdish administration since 2019, the Syrian Observatory for Human Rights said in a report.

Most of the victims are soldiers, government loyalists and Kurdish-led fighters, but the toll also incudes 627 civilians, the Britain-based Observatory said.

More than half of the 4,085 victims fell in Syria's vast Badia desert, which runs from the outskirts of Damascus to the Iraqi border.

A total of "2,744 people have been killed by the IS group since its formal collapse in 2019, in various areas of the Syrian desert," said the monitor, which relies on a network of sources inside the country.

IS fighters have killed more than 2,500 government loyalists and soldiers in the Badia since their so-called caliphate fell, according to the Observatory.

"Hardly a day goes by without bombings, ambushes, targeted operations or surprise attacks" by the jihadists in the region, the report said.

"These operations are met with periodic security campaigns carried out by regime forces and groups loyal to them deep in the desert, with... Russian warplanes targeting the desert on a near-daily basis," it added.

The group has sustained heavy damage, losing more than 2,000 fighters including top leaders since 2019, the report found.

A United Nations report released in January said IS's combined strength in Iraq and Syria was between 3,000 and 5,000 fighters, with the Badia serving as a logistics and operations hub for the group in Syria.

Syria's war has killed more than half a million people and displaced millions more since it broke out in March 2011 with Damascus's brutal repression of anti-government protests.