How are children suffering in Aleppo? The atrocities during the last few months alone are almost too many to count.

They are killed by Syrian-Russian airstrikes in East Aleppo. We occasionally glimpse the results, like the two young boys filmed in an East Aleppo suburb, grieving after the death of their brother after an airstrike in August. Days later, Syrian aircraft bombed the funeral procession. And then they bombed people who came to the rescue.

A still image from video taken October 12, 2016 of a general view of the bomb damaged Old City area of Aleppo, Syria. Video released October 12, 2016.

They are killed by mortars, rockets, and other explosive weapons launched by armed opposition groups, like those used in attacks that killed at least 22 children in West Aleppo in October.

They are killed and injured by weapons used in air attacks by the Syrian-Russian coalition. Children have been hurt by cluster bombs, which are banned by the Convention on Cluster Munitions, and by their explosive remnants – like the four-year-old girl, killed when she picked one up thinking it was a toy. Children are victims of chemical weapons, used in violation of the Chemical Weapons Convention. They suffer incendiary weapons attacks that have started raging fires and cause excruciatingly painful burns.

The hospitals where their wounds are treated are bombed by Syrian-Russian forces. On July 23, two airstrikes hit a children’s hospital, killing four newborns. In September, airstrikes hit another pediatric hospital. Airstrikes have now destroyed or incapacitated every single hospital in East Aleppo.

Their evacuation from East Aleppo for medical treatment has been blocked, including by government attacks on the only road out of the city. And in October, armed opposition groups refused a UN plea to let people out for urgent care, like a 9-year-old with heart problems and a 14-year-old with intestinal disease, after they failed to reach a deal on the evacuation with Syrian authorities.

They are being starved by government forces. The UN was last able to enter East Aleppo, where 100,000 children are besieged, on July 7. Their last remaining food supplies are about to run out. In September, when deaths from malnutrition were reported, an aid convoy delivering life-saving supplies was repeatedly attacked by Syrian-Russian airstrikes killing 18. Syrian government and opposition groups have both cut off water supplies to civilians.

They are killed when they go to school – sometimes by Syrian-Russian airstrikes, sometimes by opposition mortar and rocket attacks – like those that killed eight children at schools in western Aleppo two weeks ago as a fourth-grade class was preparing a dance routine. In East Aleppo, schools are closed, or have moved to basements, in a vain attempt to keep children safe from bombs. Across Syria, only one in three schools is still functioning.

Why don’t children’s families flee these horrors in East Aleppo? The joint Russian-Syrian offensive has dropped leaflets warning the estimated 250,000 civilians there, “If you do not leave these areas urgently, you will be annihilated. … You know that everyone has given up on you. They left you alone to face your doom.”

But many are simply too sick, weak, wounded, old, young, or afraid to escape, given that exit corridors have been repeatedly attacked, and fears of Syrian forces retaliating against them if they reach government-held territory.

Telling civilians to leave does not give the military a carte blanche to attack as though they have left. With or without a warning, attacks may be carried out only on military objectives, and must be proportionate.

Why are the children of Aleppo suffering? Because of war crimes.

How can Russian authorities relieve children’s suffering? By ending unlawful attacks and the use of unlawful weapons, and pushing Syrian forces to do the same. By allowing humanitarian aid into besieged East Aleppo, and letting civilians out. And by supporting, not blocking, calls for justice.