The International Criminal Court on Tuesday sent a 42-member team to Ukraine to probe alleged war crimes since the Russian invasion in what it called the largest such deployment in its history.
The squad comprises investigators, forensic experts and support staff and will work with Ukrainian authorities, said Karim Khan, the chief prosecutor of the Hague-based ICC.
"This represents the largest-ever single field deployment by my office since its establishment," Khan said in a statement. The ICC was set up in 2002 to probe the world's worst crimes.
The team will "advance our investigations into crimes falling into the jurisdiction of the International Criminal Court and provide support to Ukrainian national authorities," he added.
Khan thanked the Netherlands, where the court is based, for sending a "significant number of Dutch national experts" to help the mission.
The court would also work with French experts who are already in Ukraine, he said.
The ICC prosecutor announced an investigation into alleged war crimes and crimes against humanity just four days after the February 24 Russian invasion.
Khan visited Ukraine in April, travelling to the Kyiv suburb of Bucha, where AFP journalists saw least 20 bodies lying in the streets on April 2.
Khan at the time said that "Ukraine is a crime scene".
Ukraine has blamed hundreds of civilian killings on Russian forces but Russia has denied responsibility for the deaths and described the events in Bucha as fake.
- 'Law in action' -
The team of ICC investigators arriving in Ukraine now would chase up leads and collect witness testimony "relevant to military attacks", said Khan in his statement.
They would also work with Ukrainian authorities to "strengthen chain of custody with respect to hard evidence," he said.
"Now more than ever we need to show the law in action," added Khan.
"It is essential that we demonstrate to survivors and the families of victims that international law is relevant to their experience... to bring them some measure of solace through the process of justice."
Dutch Prime Minister Mark Rutte said he had discussed the issue with visiting Ukrainian Foreign Minister Dmytro Kuleba on Tuesday.
"One of the ways we support is via the Dutch forensic investigation team that this week will join the investigation into war crimes in Ukraine," Rutte tweeted.
Kuleba said there were "very positive" signs about bringing perpetrators to justice, citing the ongoing trial in the Netherlands over the shooting down of Malaysia Airlines flight MH17 over eastern Ukraine in 2014.
"The culprits will be identified and punished," Kuleba told a joint press conference with his Dutch counterpart Wopke Hoekstra.
Ukraine also "fully supports" the idea of setting up a special tribunal for prosecuting the "crime of aggression" by Russia, a crime that the ICC is not empowered to prosecute, added Kuleba.