The United Nations Security Council will hold an emergency meeting later on the humanitarian crisis in the besieged Syrian city of Aleppo.
France and the UK are calling on the body to sanction the Syrian government and Islamic State over their use of chemical weapons in attacks on civilians.
Thousands have fled rebel-held areas - but huge numbers are trapped.
Volunteer surgeon Dr David Nott has been there recently: "We cannot really fathom how bad this really is.
"I mean it is like an apocalypse, it is the worst thing you can ever face."