They are working with the International Criminal Court (ICC), which launched its investigation into possible war crimes in Ukraine in early March.
Ukraine has identified more than 600 Russian war crime suspects and has started prosecuting around 80 of them, Kyiv's top prosecutor said on Tuesday.
The list of suspects includes "top military, politicians and propaganda agents of Russia", prosecutor general Iryna Venediktova told a news conference in The Hague, The Strait Times reports.
Venediktova said Estonia, Latvia and Slovakia had decided to join an international investigation team in Ukraine, which was originally formed by Ukraine, Lithuania and Poland in March to enable the exchange of information and investigation into suspected war crimes and crimes against humanity.
They are working with the International Criminal Court (ICC), which launched its investigation into possible war crimes in Ukraine in early March.
ICC prosecutor Karim Khan office has deployed a team of 42 investigators, forensic experts and support personnel to Ukraine and Khan on Tuesday said the ICC was "working toward opening an office in Kyiv" to support the investigations.
Venediktova said international support was vital to Ukraine's efforts to investigate all possible war crimes.
"We should collect and protect everything in the right way. It should be acceptable evidence in any court", the prosecutor said.
Russia has denied targeting civilians or involvement in war crimes while it carries out what it calls a "special military operation" in Ukraine.
The prosecutor’s comments come as a Ukrainian court sentenced two captured Russian soldiers to 11 and a half years in jail on Tuesday for shelling a town in eastern Ukraine, the second war crimes verdict since the start of Russia's invasion in February.
Alexander Bobikin and Alexander Ivanov, who listened to the verdict standing in a reinforced glass box at the Kotelevska district court in central Ukraine, both pleaded guilty last week.