The Prosecutor General's Office (PGO) of Ukraine says the law enforcers have identified 54 foreign mercenaries who have taken part in hostilities against Ukraine in Donbas on the side of the so-called "DPR" and "LPR" (the self-proclaimed "Donetsk and Luhansk People's Republics").

Kyiv wants to use this information to prove the fact of Russia's waging of war in Donbas and financing of terrorism internationally, the PGO told journalists, as reported by the Ukrainian-language service of Germany's Deutsche Welle (DW).

In early July, Ukraine's Chief Military Prosecutor Anatoliy Matios told TV Channel 112 Ukraine that the PGO over the four years of the war in Donbas had identified more than 50 foreigners fighting on the side of the militants from the "DPR" and "LPR."

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Most of them are Italians, but there are also Frenchmen, Spaniards, Serbs, Finns, Czechs and even one U.S. citizen. Kyiv has sent the list of them to the International Criminal Court (ICC).

The Office of the Prosecutor of the ICC in The Hague did not comment on the reports by Matios, referring to regulations of confidentiality, stipulated in the Rome Statute.

The PGO's statement demonstrates that Ukraine is suing Russia in two courts, namely the International Criminal Court and the UN International Court of Justice, with which Ukraine has already lodged a relevant lawsuit, the publication wrote.

Expert from Max Planck Institute for Comparative Public Law and International Law Matthias Hartwig told journalists that it would not be easy to prove Russia's guilt at the ICC for war against Ukraine.

He says it is problematic because Russia has not ratified the Rome Statute, which regulates the issue. That is, Russia's leader who orders to invade cannot be brought to justice in court. Unless, of course, the UN Security Council takes a respective decision, but this is impossible.

Moreover, it is virtually impossible to bring foreign mercenaries to justice through international courts, according to the expert. Only aggressive war, serious war crimes, genocide, and crimes against humanity are the grounds for considering a claim at the ICC. But so far, there are no decisions by the ICC on the Donbas war.