The US has urged the Syrian government to allow immediate aid convoys to starving civilians cut off in rebel-held suburbs of Damascus.
Washington said the army’s months-long siege left many people in desperate need of food, water and medicine.
It also cited “unprecedented reports” of children dying of malnutrition just a few kilometres from President Bashar al-Assad palace.
The Syrian army has warned the rebel-held areas must surrender or starve.
At least three of Damascus’ suburbs – Yarmouk, Eastern Ghouta and Moudamiyah – have been besieged by government forces for several months.
The situation has become so desperate that earlier this week Muslim clerics issued a religious ruling allowing people to eat cats, dogs and donkeys just to survive.
Those animals are usually considered unfit for human consumption in Islam.
In a statement on Friday, US State Department spokeswoman Jen Psaki said: “We call on the Syrian regime to immediately approve relief convoys.”
And she warned that “those who are responsible for atrocities in the Damascus suburbs and across Syria must be identified and held accountable”.
She added that in Moudamiyah “people have been without basic necessities for nearly a year, and the regime’s deliberate prevention of the delivery of life-saving humanitarian supplies to thousands of civilians is unconscionable”.
Footage obtained by the BBC from Yarmouk showed families struggling to find enough to eat.
An 11-year-old boy in the suburb, who had seen many of his friends die, said: “We bored of this. If they (government troops) want to attack us with chemical weapons – then just do it! But can they make them with the smell of bread so we can die happy?”
Syrian activists say they are now starting to record the first deaths of complications caused by malnutrition.