An advance team left the International Criminal Court (ICC) in The Hague for the Ukraine region on Thursday to start investigating possible war crimes, its top prosecutor told Reuters in an interview.

Their departure comes hours after Prosecutor Karim Khan announced he would start collecting evidence as part of a formal investigation launched after Russia's full-scale invasion of Ukraine on Feb. 24.

"Yesterday I formulated a team and today they are moving to the region," Khan said.

Khan said his office would be examining possible war crimes, crimes against humanity and genocide by all parties in the conflict.