ITV News team Peter Smith, Mike Field, John Angier, and Kseniia Kozhushko film in the villages devastated by war
ITV News has heard accounts of Ukrainian civilians and prisoners being killed by Russian soldiers retreating from occupied towns and villages.
It comes as Ukraine's top prosecutor said the bodies of more than 1,200 civilians have so far been discovered in areas reclaimed from Russian troops.
Our team travelled to several villages close to the town of Makariv, west of Kyiv, and heard repeated claims of men of fighting age being shot in the head.
Olena Marzhunko says she witnessed her nephew being shot dead.
"I was standing in my garden and I saw three young boys walking over here.
"They had their hands up, Sasha was at the front. Their hands were still up, but the Russians still shot them".
What we are witnessing is war crimes, says ITV News Correspondent Peter Smith
Ihor Savran's body was found in a barn after Russian troops were ousted.
His mother, Anastasia, says Russian soldiers dragged him out of their house in front of her, the next time she saw him, it was to identify his body.
"He was killed by a shot in his right ear, he was lying down, like he was sleeping when he was killed".
She says she found him with his hands folded beneath his head.
Ukraine has accused Russia of atrocities against civilians in Bucha and other places near Kyiv, where hundreds of slaughtered civilians, many with their hands bound and signs of torture, were found after Russian troops retreated.
The Kremlin continues to deny its soldiers have committed war crimes.
An update from the UK Ministry of Defence on Sunday night said "further evidence of alleged Russian war crimes continues to emerge following Russian withdrawal from northern Ukraine.
"This includes the reported discovery of a makeshift grave containing deceased Ukrainian civilians near Burzova."
It added: "Allegations of sexual violence perpetrated by Russian military personnel persist."
On Sunday, a senior US official said Russia has appointed a new commander to oversee its invasion of Ukraine. The official, speaking on condition of anonymity, said Russia had turned to one of its most experienced military officers, Gen. Alexander Dvornikov.
The 60-year-old general has a record of brutality against civilians in Syria and elsewhere.
It comes as Russia’s military is lining up more firepower ahead of an expected showdown in eastern Ukraine - one that could become a decisive period in a war that has flattened cities and killed untold thousands.
Experts say a full-scale offensive in the east could start within days, though questions remained about the ability of Russia’s depleted and demoralised forces to conquer much ground.
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Ukraine’s Deputy Prime Minister Iryna Vereshchuk said more civilians were expected to leave Mariupol on Sunday.
Evacuations are also planned from Berdyansk, Tokmak and Enerhodar in the south and Sieverierodonetsk, Lysychansk, Popasna and Rubizhne in the east.
Mariupol, a strategic port city on the Sea of Azov, has been besieged by Russian forces for nearly six weeks - cut from food, water and power supplies and pummelled by relentless bombardment.
The death toll stands at at least 5,000, according to local officials.
Ukrainian authorities have urged civilians in the east to evacuate in the face of an imminent Russian offensive. They accused Russia of killing 52 people on Friday at the train station in the eastern city of Kramatorsk as they were preparing to evacuate.