What is a war crime, and could Putin be prosecuted over Ukraine?

Ukrainian President Volodymyr Zelensky has described an attack on a maternity and children's hospital as a "war crime".

It may not seem like it, but "even war has rules", as the International Committee of the Red Cross puts it.

These are contained in treaties called the Geneva Conventions and a string of other international laws and agreements.

What is a war crime?

Civilians cannot be deliberately attacked - nor can the infrastructure that is vital to their survival.

Some weapons are banned because of the indiscriminate or appalling suffering they cause - such as anti-personnel landmines and chemical or biological weapons.