UPDATE: The Syrian government refused a United Nations-brokered truce on Sunday. The deal would have given the eastern part of Aleppo autonomy, The Associated Press reports.
Foreign Minister Walid al-Moallem said the deal would leave 275,000 people "hostages to 6,000 gunmen."
WATCH | What's left of an Aleppo hospital
Intensified attacks on eastern Aleppo has left the besieged Syrian city without a single functioning hospital.
Barrel bombs and airstrikes killed at least 48 people on Saturday, according to the Syrian Observatory for Human Rights. The British-based watchdog, which relies on a network of local activists, says an estimated 180 people died this week.
The World Health Organization says every one of the city's makeshift hospitals is out of service. Syrian warplanes have also targeted schools and homes, and on Wednesday, struck the city's main blood bank.
After nearly four weeks of relative calm in the besieged city, warplanes resumed strikes across northern Syria.
Russia, a key ally of Syrian President Bashar al-Assad, acknowledged its forces launched a new offensive in rebel-held areas of Idlib and Homs provinces, but denied involvement in Aleppo.
The city's 250,000 residents have lived under a siege since July when government forces took control of the only supply road leading out of Aleppo. In September, the Syrian regime announced plans to take back the city following months of failed negotiations between Russia and the U.S.
The United States condemns in the strongest terms these horrific attacks against medical infrastructure and humanitarian aid workers.
The United States on Saturday issued a statement calling the attacks on hospitals "heinous" and warning the Syrian regime and its Russian allies of "immediate and long term consequences."