Ukrainian President, Volodymyr Zelensky, has warned that the worst atrocities committed by Russian troops departing from the north of the country are yet to be discovered.
He said the town of Borodyanka may have suffered more than others.
Horrific images of bodies in streets in towns such as Bucha have generated shock and condemnation worldwide.
Ukrainian intelligence officials said Russian units based in the region would be sent back to eastern Ukraine.
The 64th motorised rifle brigade – which they alleged committed atrocities in Bucha – would return to the conflict within weeks, probably to the Kharkiv area, they said.
Russia denied killing civilians, and without evidence said Ukraine staged the scenes.
The Ukrainian government started a war crime investigation after it said the bodies of 410 civilians had been found in areas around Kyiv.
Some were discovered in mass graves while others had their hands tied and had apparently been shot at close range.
Officials in Kyiv also accused Russian forces of killing a village head, her husband and her son in the village of Motyzhyn for aiding Ukrainian troops in the area.
There were also reports of at least three apparently tortured bodies in the town of Konotop in another northern region, Sumy.
The images from Bucha prompted US President, Joe Biden, to call for his Russian counterpart, Vladimir Putin, to be tried for war crimes.
His intervention came as new satellite photos by the earth observation company, Maxar, showed bodies lining Bucha’s streets during its occupation by Russian forces.
Foreign Minister, Dmytro Kuleba, told a news conference in Warsaw on Monday that the killings were the “tip of the iceberg” and demanded more severe sanctions against Russia.
In a BBC interview, he cited the desperate situation in the southern town of Mariupol, which has been under Russian bombardment for weeks.
“What we’ve seen in recent weeks is that Russia is much worse than ISIS (the Islamic State group) when it comes to its atrocities and massacres,” he said.
In his nightly address to the Ukrainian people, Mr. Zelensky said things were being done throughout the region, north of Kyiv, that people had not seen since the Nazi occupation.