Troops loyal to Syrian dictator Bashar al-Assad and foreign militias under Iranian command swept into eastern Aleppo on Monday, recapturing nearly all of the city’s opposition-held areas and seizing the citadel of the Syrian revolution.

The triumphal takeover followed a day of intense bombing of houses and apartment buildings, destroying so many that it was impossible to determine the death toll. The neighborhoods of Bustan al-Qasr, al-Kallasa, al-Farod and al-Salhin in the Old City, as well as Sheikh Saed, in the southern district, are all now under regime control.

The United Nation’s top human rights official on Tuesday charged the U.S. and other countries with collectively wringing their hands in the face of the “wanton slaughter of men, women and children” in Aleppo and pleaded for the world to take measures to protect those fleeing the Russian and Syrian regime onslaught. The U.N. had received credible reports of scores of civilians being killed either by intense bombardment or summary executions by pro-government forces. Zeid Ra’ad al Hussein, the High Commissioner for Human Rights, said in a statement. “Dozens of bodies reportedly litter the streets of a number of east Aleppo neighborhoods, with residents unable to retrieve them due to the intense bombardment and fear of being shot,” Hussein said. He added that the U.N. had reports that at least 82 civilians, including 11 women and 13 children in four neighborhoods – Bustan al-Qasr, al-Ferdous and al-Kallaseh and al-Saleheen. Decrying “the crushing of Aleppo, the immeasurably terrifying toll on its people, the bloodshed, the wanton slaughter of men, women and children, the destruction,” the Jordanian-born U.N. official warned, “We are nowhere near the end of this cruel conflict.” “What can happen next, if the international community continues to collectively wring its hands can be much more dangerous.” Hussein said the slaughter in Aleppo could repeat itself in Douma, Raqqa and Idlib, referring to other opposition-held areas in the war-ravaged country. “We cannot let this continue.”   The White Helmets, a volunteer rescue group, described Aleppo as being “like hell.” The streets and destroyed buildings “are full of dead bodies,” said a tweet by one of its volunteers. The rescue service was reported to be totally paralyzed by the assault. The head of the group’s Aleppo branch, Ammar al-Salmo, said on Al Jazeera television that many old men died of the cold weather in eastern Aleppo. More than 100 unaccompanied children were reported to be trapped in a building under heavy bombardment in eastern Aleppo, according to UNICEF, the U.N. agency responsible for child welfare said, quoting an unnamed doctor in the city, Reuters reported. The head of the Aleppo local coordinating committee told regime forces had captured the remaining food supplies in eastern Aleppo and there are no functioning bakeries and no bread, the Turkish Anadolu news agency reported.

Syrian army spokesman Brig. Gen. Samir Suleiman countered that the U.N. was lying. “These are false claims. The Arab Syrian army can never do this and we have never done it in our army’s history.” Yesterday, the official Syrian news agency SANA instead lay blame for atrocities in Aleppo on the rebels, alleging that eight people were killed and 47 were injured in regime-held areas after the opposition bombed them. Most of the victims were women and children, according to the agency.

Abdullah Othman, the head of the Consultative Council in the Levant Front, one of the largest rebel groups in Aleppo, said this morning that the opposition was still in possession of six neighborhoods, including Salaheddine, once the sight of some of the fiercest urban combat the Syrian civil war had witnessed. “Last night we were able to reinforce our new defense lines and to build some blast walls on the new borders,” Othman told The Daily Beast today, speaking from the border town of Azaz. “Today the regime forces tried to sweep through our new defense lines but they haven’t been able to do so yet. But the problem is the barbaric, unprecedented bombardment and shelling that you can’t even imagine.”

Civilians were apparently crammed into whatever buildings still remain in the tiny quarters yet to be recaptured by the Assadists, but many were left outside in the streets, owing to lack of space. It is here, in broad daylight, Othman said, that men, women and children were being cooked alive by barrel bombs dropped right where they stood.   And those who survive the air raids could not be helped. “Women and children — their screams can be heard underneath the rubble. Unfortunately, there is nothing we can do to get them out. Everyone is panicking. There is great fear. Everyone can only think of himself, not about others.”

Yesterday, some residents who couldn’t take the bombardment anymore fled toward regime controlled areas, according to Othman. “Seventy-nine of them were executed at the barricades. The rest — everyone under 40 — were taken to warehouses that look more like internment camps. They face an unknown fate,” he said. “This morning 20 women committed suicide in order not to be raped.”

The last hope of the besieged rebels, most of whom seem to have withdrawn in the face of certain defeat, had been to receive reinforcements or resupplies from their counterparts in the southern and western suburbs. That option has now been foreclosed upon as these routes are completely interdicted by the regime.

Enab Baladi, a Syrian opposition news channel, said regime artillery attacked the six neighborhoods remaining in rebel hands with 40 shells and its ground forces – mostly Shiite militias under Iranian command – are attacking from four directions.

Activists and residents of the ever-dwindling opposition pocket, an urban islet of about five square kilometers and home to as many as 100,000 people, spent the last 24 hours signing off from social media, asking journalists to tell their story, and warning of their impending demise.

The Daily Beast was able to get in touch with Abdulkafi Al-Hamdo, a university teacher in the besieged city, on Monday evening. The brief conversation was as follows:

TDB: “I hope you’re safe.”

AA: “I don’t think I will be tomorrow.”

TDB: “Do you expect all the remaining besieged neighborhoods will fall by tomorrow?”