The bombardment targeted rebel-held districts in eastern Aleppo and opposition communities in the surrounding countryside. The Syrian Observatory for Human Rights, which opposes the government and tracks the conflict from Britain, said 72 people had been killed in all of Aleppo Province, including 24 women and children. But most of the dead were in the city itself.

Mr. Le Mesurier reported 95 dead and 147 people hospitalized in Aleppo city alone.

Rescue workers shared numerous videos of men digging children out of piles of debris and entire neighborhoods reduced to rubble.

Hanaa Singer, the representative for Unicef in Syria, said in a statement that attacks had damaged the pumping station that provides water to eastern Aleppo, where 250,000 residents are surrounded by government troops. In retaliation, she said, a pumping station in the city’s eastern side was shut off, stopping water from flowing to 1.5 million residents in the city’s western side.

The population would have to rely on well water, which is often contaminated and would raise the risk of outbreaks of disease, she sad.

Ammar al-Salmo, head of the Aleppo branch of Syria Civil Defense, a volunteer rescue organization, said that three of his group’s centers had been bombed and that some of their rescue vehicles had been knocked out.

“It is as if Russia and the regime used the truce only to maintain their weapons and plan on next targets,” Mr. Salmo said from Aleppo. “It is like doomsday today in Aleppo.”