BEIRUT/GENEVA: Syria’s army declared victory over Daesh (ISIS) Thursday, saying its capture of the militants’ last town in the country marked the collapse of their three-year, hard-line reign in the region.

The announcement came as U.N. humanitarian adviser Jan Egeland told reporters that 400,000 civilians besieged in the enclave of Eastern Ghouta face “complete catastrophe” because aid deliveries are blocked and hundreds of people need urgent medical evacuation.

The Syrian army and its allies are still fighting Daesh in desert areas near Albukamal, the last town the militant group had held in Syria, near the border with Iraq, the army said.

But the capture of the town ends Daesh’s era of territorial rule over the so-called caliphate that it proclaimed in 2014 across Iraq and Syria and in which millions suffered under its hard-line, repressive strictures.

Yet after ferocious defensive battles in its most important cities this year, where its fighters bled for every house and street, its final collapse has come with lightning speed.

Instead of a battle to the death as they mounted a last stand in the Euphrates valley towns and villages near the border between Iraq and Syria, many fighters surrendered or fled.

“There’s some fighters left but they’re few. Small numbers is all I can say,” said a Syrian army commander of the remaining militants near Albukamal. “Some were killed and some ran away. They went toward eastern or northern villages.”

In Albukamal, the militants had fought fiercely, a commander in the pro-Syrian government military

alliance said. But it was captured the same day the assault began.Pro-Syrian media reported the town was liberated. Al-Ikhbariya TV’s journalist reported from the road to the town, joyfully breaking out on camera: “Daesh is finished. Live.”

This sealed “the fall of the terrorist Daesh organization’s project in the region,” an army statement said.

The fate of its last commanders is still unknown – killed by bombardment or in battle, taken prisoner but unidentified, or hunkered into long-prepared hideouts to plot a new insurgency.

Also Thursday, U.N. humanitarian adviser Egeland spoke of the rapid-growing humanitarian crisis in besieged Eastern Ghouta.

“Nowhere is it as bad as in Eastern Ghouta,” Egeland said of the area, which is surrounded by the army. “I feel as if we are now returning to some of the bleakest days of this conflict again.”

Seven people have died because they were not evacuated and 29 more were at imminent risk, including 18 children, he told reporters in Geneva after a regular meeting of the U.N. humanitarian taskforce on Syria.

“We cannot continue like that. If we only get a fraction of what is needed it will be a complete catastrophe,” he said.

“What about a ceasefire now in this area and a green light to all medical evacuations?” he asked.

Russian, Syrian and U.N. officials had met in Damascus to try to break the deadlock, both for Eastern Ghouta and for about 55,000 civilians stranded on the Jordanian border in a desolate area known as the Berm.

“The first meeting still hasn’t produced at all the concrete results that were needed but it is our strong feeling that the Russian Federation wants us to get the access and wants to help us so we are hopeful that this trilateral mechanism will yield results.”