Live updates: follow the latest news on Russia-Ukraine
Ukrainian investigators have identified more than 8,000 cases of suspected war crimes since Russia's invasion, Ukraine prosecutor general Iryna Venediktova told a German TV channel on Thursday.
"It's actually 8,600 cases only about war crimes, and more than 4,000 cases that are connected with war crimes," Ms Venediktova told the Deutsche Welle broadcaster.
She has been investigating and tallying the mounting cases of suspected crimes by Russian forces since their invasion of Ukraine on February 24.
There are now more than 8,000 investigators gathering evidence, she said, including state security services, national police and foreign investigators.
The alleged crimes documented include "killing civilians, bombing of civilian infrastructure, torture" and "sexual crimes" that are being reported in the "occupied territory of Ukraine", Ms Venediktova said.
They are also using "radio connections and audio connections of the occupants".
At a UN session in New York on Wednesday, a senior US official also spoke of credible information that war crimes might have been committed in Donetsk.
"We now have credible information that a Russian military unit operating in the vicinity of Donetsk executed Ukrainians who were attempting to surrender, rather than take them into custody," said Beth Van Schaack, US ambassador at large for global criminal justice.
"If true, this would be in violation of a core principle of the law of war."
Ms Venediktova has spent the past two months travelling through unoccupied Ukraine gathering evidence.
Her office also announced on Thursday that 10 Russian soldiers were under investigation on suspicion of war crimes in Bucha, where dozens of bodies in civilian clothes were found after Russian troops retreated.
Ms Venediktova said the cases would be prosecuted in Ukraine's domestic courts. But the highest prize would be conviction in an international court.
Ukraine is not a member of the International Criminal Court but it has accepted its jurisdiction in the past, leaving the door open to a tribunal.