GWEN IFILL: The rapid deterioration of the situation in Aleppo, Syria, accelerated today. Two hospitals were bombed, among dozens of other targets.

UNICEF reports that nearly 100 children are among the hundreds killed since last Friday.

And harsh words resumed at the United Nations, as the U.S. threatened to cut off all cooperation with Russia over Syria.

Hari Sreenivasan reports.

And a warning: Images in this story may disturb some viewers.

HARI SREENIVASAN: Blood mingled with fresh bread on the streets of East Aleppo, the remains of a bakery, and its customers, struck this morning amid the ongoing, thunderous bombardment.

In the terrible stillness after the attack, a medical worker told of the carnage.

MAN (through translator): The Russian planes started dropping missiles and rockets. People who were coming to get bread from the bakery were martyred. There are a number we cannot reach due to the number of shells that were dropped.

HARI SREENIVASAN: And, nearby, two hospitals referred to by code names M2 and M10 to hide their locations were also hit. They are supported by the Syrian-American Medical Society, an NGO.

On a social media chat group monitored by the "NewsHour," medical personnel and activists said only six hospitals remain operational. Those six hospitals serve a quarter-of-a-million people. Now just two of them can perform surgery.

A worker at one hospital gave a guided video tour of the destruction.

MAN (through translator): At 4:00 this morning, the barrel bombs surprised us. This is where they landed, a total targeting, major damage here.

HARI SREENIVASAN: Activists say that, in the last eight days, there have been 1,700 airstrikes, and at least 400 people killed.

The onslaught triggered new condemnation at the U.N. Security Council today. Secretary-General Ban Ki-Moon leveled his harshest judgment to date, blaming Russia and the Assad regime in all but name.

BAN KI-MOON, Secretary-General, United Nations: They know they are committing war crimes. Imagine a slaughterhouse. This is worse. Even a slaughterhouse is more humane.

HARI SREENIVASAN: Russia's deputy envoy said the scenes from Aleppo were the work of rebel propagandists.

EVGENY ZAGAYNOV, Deputy UN Ambassador, Russia (through translator): We call for a rejection of provocative rhetoric and to focus all of our attention and forces on bringing an end to conflict in Syria. And we have a very good basis for this based in Russian-American cooperation.

HARI SREENIVASAN: But that cooperation, already tenuous, may be ending. Today, Secretary of State Kerry told Foreign Minister Sergei Lavrov in a phone call that the U.S. holds Russia responsible, and will cease cooperation with Moscow on Syria if the bombing doesn't stop.

Lavrov said it's the U.S. that must do more. The western government- controlled sectors of Aleppo, where more than a million Syrians live, do come under attack from rebels, but nothing on the scale of what's happening in the east. Syrian army ground units have now progressed into the rebel-held sectors. Syrian state TV showed its forces fighting yesterday in a central area.

MAN (through translator): We entered Farafrah District and broke the first defense line of the armed terrorist groups in the area.

HARI SREENIVASAN: Breaking those lines also means breaking the people who live there with strikes from above. The vast majority are trapped civilians.

This video, also filmed yesterday, is of the crushing aftermath of a bombing and a father retrieving his lifeless son.

Those screams echoed within the sanctums of the Vatican today, compelling Pope Francis to warn of a higher judgment that awaits the bombers of Aleppo.

POPE FRANCIS, Leader of Catholic Church (through translator): I make an appeal to conscience of those who are responsible for the bombings, who will one day will have to face the judgment of God.

HARI SREENIVASAN: That reckoning is still to come. But, for now, no more horrendous sense of the sheer despair can be found than in the panicked cries of this man filmed by the BBC.

His name is Mohammed Janidi, and he calls out for his son Husam lying in a body bag to get up. As the body is taken away, Mohammed is heard to say: "His mother is going to go crazy. She will go crazy."

For the "PBS NewsHour," I'm Hari Sreenivasan.