The incident took place on March 27 in the village of Stepanki outside the regional capital Kharkiv, when occupying Russian forces opened fire on a house from a tank, killing two men and a women, Ukraine's prosecutor general's office said on Telegram.

Kharkiv police and witnesses said four people were killed and two wounded. The discrepancy could not be immediately explained.

An investigation into a war crime and premeditated murder has been opened, according to prosecutors.

Witnesses interviewed by AFP said the six people who lived in the house were drinking tea in the courtyard when a Russian tank approached.

"They started going into the house to hide," said Olga Karpenko, 52, whose daughter was among those killed. The tank took aim and fired at them as they entered the house.

"Four people died, two were injured. My daughter died from a shrapnel wound in the back of her head," Karpenko said.

Local resident Denys, 40, said he saw the barrel of the tank turn towards him.

"Someone said: let's go hide inside the house," Denys remembered. "I entered last and as soon as I entered the tank fired. Everything collapsed, I couldn't see anything. I got out as soon as I could and ran behind the house."

The neighbours buried the dead in the back garden of the house, and with the village back under Kyiv's control, their bodies were exhumed on Wednesday.

Prosecutors published photos of a peach-coloured two-storey building, its windows blown out and the front partially destroyed. Nearby, three crosses made of sticks stood over a grave site.

Since Moscow launched a large-scale invasion of Ukraine on February 24, Kyiv has accused Russian troops of multiple war crimes in the cities and towns they occupied, including murder, torture and rape.

On Thursday, CNN released what it said was security camera footage showing two Ukrainian civilians shot in the back by Russian soldiers near a car dealership outside of Kyiv in mid-March.