Ukrainian President Volodymyr Zelensky has demanded a special tribunal to hold Russia accountable for its "crime of aggression" which, unlike other war crimes, is not fully covered by the International Criminal Court.
The ICC in The Hague is currently probing possible war crimes and crimes against humanity committed during the war in Ukraine, but it has no mandate to pursue the broader crime of aggression.
It has issued an arrest warrant for Russia's Vladimir Putin over a war crime charge, linked to the alleged deportation of Ukrainian children.
We look at the different categories of the most serious crimes known to man.
- War crime -
War crimes are serious violations of international law against civilians and combatants during armed conflict.
The parameters of what constitutes a war crime are set out in Article 8 of the 1998 Rome Statute that established the ICC.
It defines them as "grave breaches" of the 1949 Geneva Conventions covering more than 50 scenarios, including killing, torture, rape and the taking of hostages as well as attacks on humanitarian missions.
Article 8 also covers deliberate attacks on civilians or "towns, villages, dwellings or buildings which are undefended and which are not military objectives" as well as the "deportation or transfer of all or parts of the population" of an occupied territory.
Ukraine's authorities say they have received thousands of complaints of alleged war crimes by Russian forces since the invasion began on February 24, 2022.
- Crime against humanity -
The notion of such a crime was first laid down on August 8, 1945, and codified in article 7 of the Rome Statute. It involves "a widespread or systematic attack directed against any civilian population" including "murder" and "extermination" as well as "enslavement" and "deportation or forcible transfer".
Crimes against humanity can occur in peace time and include torture, rape and discrimination, be it racial, ethnic, cultural, religious or gender-based.
- Genocide -
Genocide as a legal concept dating back to the Nuremburg trials of Nazi war criminals, with Polish-Jewish lawyer Raphael Lemkin coining the term to describe the Nazi extermination of six million Jews.
The crime of genocide was formally created in the Genocide Convention of 1948 to describe "acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group".
Genocide is a "very specific international crime" which is difficult to prove, says Cecily Rose, professor of international law at the University of Leiden in the Netherlands, noting that it demands proof of the "mental motivation" behind it.
- Crime of aggression -
The ICC added a crime of aggression to its remit in 2017 to include attacks on "the sovereignty, territorial integrity or political independence" of another country.
The offence aims to ensure that political and military leaders are held accountable for invasions, but it cannot be used against the dozens of ICC members that have not recognised the court's jurisdiction, including Russia, nor against non-members. Ukraine is a non-member, but accepts the court's jurisdiction over the crimes.
