International Criminal Court prosecutor Karim Khan said Monday he was launching an investigation on the "situation in Ukraine" following Russia's invasion.
"Today I wish to announce that I have decided to proceed with opening an investigation into the situation in Ukraine, as rapidly as possible," Khan said in a statement.
"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" since 2014, he said.
"Given the expansion of the conflict in recent days, it is my intention that this investigation will also encompass any new alleged crimes falling within the jurisdiction of my office that are committed by any party to the conflict on any part of the territory of Ukraine."
Khan had said last week that The Hague-based court had received many queries "with respect to the crime of aggression" but could not exercise "jurisdiction over this alleged crime" as neither Russia nor Ukraine were signatories to ICC's founding Rome Statute.