This has been a recent Russian tactic following setbacks on the battlefield, and its impact is starting to be felt more acutely as winter sets in."Put simply, this winter will be about survival," Dr Kluge told a news conference in the Ukrainian capital, Kyiv.The WHO defines an attack as involving violence as well as threatened violence against hospitals, ambulance and medical supplies.The warnings come as snow has fallen across Ukraine and temperatures have dropped below freezing.Elsewhere in the war, Ukrainian prosecutors have given details of what they have found in four alleged torture chambers in Kherson after Russian troops left the southern city."