The Syrian Observatory for Human Rights announced on Monday that ISIS had regained control of the city of Albu Kamal, their last stronghold in Syria, after setting up an ambush against Iran-backed factions. The factions had last week declared that they had seized the city and forced ISIS to withdraw. Fighters from Lebanon’s “Hezbollah” in Syria, who joined forces with Iraqi militias crossing the border into Syria, were taken by surprise by terrorists hiding inside tunnels in the heart of the city they said they had taken on Wednesday, tribal leaders, residents and the Observatory said. “Hezbollah” and the Iraqi groups had launched a ground offensive on the city, in Syria’s eastern Deir al-Zour province where the Euphrates river meets, after months of mainly heavy Russian bombardment against the city that killed dozens of civilians and caused widespread destruction. “ISIS began surprise attacks with suicide bombers and rocket attacks after the Iranian factions were duped that it had left the city,” said Qahtan Ghanam al Ali, a tribal leader in touch with relatives. The Syrian regime forces had on Thursday declared victory over ISIS. It said the capture of Albu Kamal marked the collapse of the organization’s three-year reign in the region. “These militant attacks lead to big human losses in the ranks of fighters supporting the regime,” the UK-based Observatory said. On Sunday, jets believed to be Russian intensified their third day of bombing of Albu Kamal and its outskirts, with at least 50 civilians, mostly women and children, killed since Friday, the monitor and residents said. In retaliation for their losses, Iranian factions, who were forced to withdraw shelled villages east of the city where hundreds of families who fled Albu Kamal had found temporary refuge, the monitor continued. In one air strike on the town of Sukariya, east of the city, at least 30 people were killed, mostly women and children from three families, two former residents of the city in contact with relatives said. Military experts and Syrian opposition figures say Russia has stepped up a “scorched earth” policy in the province with its aerial bombing in recent months to secure a rapid military victory at any price for its military and its allies.