Russia Ukraine War: Will Putin press 'nuclear button'?

Kiev's defence ministry claims that more than 5,000 Russian soldiers have been killed in the first four days of fighting in Ukraine

In a statement posted to Facebook, Ukrainian officials said approximately 5,300 Russian troops have been killed, and claimed that 191 tanks, 29 fighter jets, 29 helicopters and 816 armoured personnel carriers have been destroyed by Ukraine's forces.