He said in a statement that there was “a reasonable basis to proceed with opening an investigation”.

Neither Russia nor Ukraine are ICC members, but Kyiv has accepted the court’s jurisdiction.

He added: “In particular, I am satisfied that there is a reasonable basis to believe that both alleged war crimes and crimes against humanity have been committed in Ukraine”.

Mr Khan said authorisation from the Pre-Trial Chamber of the court must now be obtained. Alternatively an ICC state party could refer the case to the ICC.

He said: “I will also be asking for the support of all states parties and the international community as a whole as my office sets about its investigations. I will be calling for additional budgetary support, for voluntary contributions to support all our situations, and for the loan of gratis personnel.

“The importance and urgency of our mission is too serious to be held hostage to lack of means.”