Ukraine's top prosecutor said his office had opened criminal proceedings relating to Russian missile strikes that bombarded Kyiv earlier this week.
Prosecutor General Andriy Kostin described the strikes since Monday as “a classic act of terror” by Russia.
He said the 112 Russian missile strikes, Moscow's biggest aerial offensive since the start of its invasion on February 24, had killed 17 people and injured 93.
“All of the hits of every missile, every drone, every damage of civil infrastructure, every Ukrainian who was killed or wounded by these missile attacks, all of them are documented and criminal proceedings were registered and opened,” he said.
He said war crime cases have been started against 186 people since the war started and 10 have now been convicted, but that many of the suspects were in Russia.
“We have identified them but we do not know where they are,” he said.
“We have victims and they are waiting for justice. We cannot just stop cases because we do not know where they are.”
He made the comments at a joint press conference with International Criminal Court (ICC) prosecutor Karim Khan and the president of Europe's crime agency Eurojust, Ladislav Hamran.
Mr Khan said Ukraine could extradite Russian war crimes suspects to the International Criminal Court even though Moscow is not a member.
Kyiv authorities could send Russians to The Hague-based court if trials could not take place in Ukraine for legal reasons, Mr Khan said.
Russia refused to join the ICC when the court was set up in 2002 to try people for offences including war crimes, crimes against humanity and genocide.
“Legally yes it wouldn't represent an obstacle to our jurisdiction,” Mr Khan said.
“Certainly if there was a need … and there was a reason why those trials could not take place in Ukraine, whether it's because of some legal additional provisions that we have or not, I am sure that we would get the co-operation from Ukraine,” he added.
The ICC opened its own investigation into the war in Ukraine shortly after Russia invaded, but has said it is keen for Ukraine to bring suspects to justice where possible.
Mr Khan would not say when the ICC expects to file its own first charges, saying he would wait until the “evidence is sufficient.”
“We are moving forward, we have focus, but I will make announcements at the right time,” he said.
The prosecutor's office has 28 investigative teams on the ground in the recently liberated regions, where Mr Kostin said retreating Russian troops had left evidence of illegal detention and torture of civilians and illegal deportations.
In the recently liberated Kharkiv region of eastern Ukraine prosecutors had found at least 11 burial sites, including one mass grave near the town of Izium. and had exhumed 457 bodies across the sites, Mr Kostin said.
An additional two mass graves were found in the Lyman region with about 154 people — Ukrainian soldiers and civilians — buried there, he added.
Russia has repeatedly denied deliberately attacking civilians in Ukraine. Moscow also denies violating international law and has dismissed allegations by Kyiv that Russian soldiers have carried out war crimes.