At least two bodies were discovered Sunday in a manhole at a petrol station west of Kyiv, an AFP reporter saw.
The bodies appeared to be clad in a mix of civilian and military clothing.
AFP saw police and soldiers at the petrol station, located on a highway near the village of Buzova, using a tanker to suck water out from the manhole.
There appeared to be two bodies inside, one under a sleeping mat.
Ukraine says it has discovered a trail of civilian bodies in towns outside Kyiv from where the Russian army retreated, accusing Moscow of war crimes.
A distraught woman appeared at the manhole and peered inside, before breaking down and clawing the earth.
"My son, my son," she wailed, recognising the body from the distinctive footwear.
Police are awaiting demining teams before recovering the bodies.
The improvised grave is at the back of a destroyed motorway petrol station.
Tank marks are visible on the road and there are two destroyed tanks near the station.
Police were unfurling crime scene tape around the scene.