Satellite images taken by a US firm of a large Russian military convoy near Ukraine's capital, Kyiv, show it has "largely dispersed and redeployed".
The convoy was last seen near Antonov Airport, north-west of Kyiv, and its movement could signal a renewed push towards the city.
The firm that took the photos, Maxar Technologies, said parts of the convoy were in positions in surrounding towns.
Other parts are further north, with artillery now in firing positions.
Blasts in cities on opposite sides of the country were reported on Friday morning:
- An airfield and jet engine factory were targeted in Lutsk, in the north-west
- In Dnipro, a major stronghold in central eastern Ukraine, one person was reported dead in air strikes
- Explosions also hit airfields at Ivano-Frankivsk, in the south-west, according to Russian defence officials
"Ukrainian big cities are again subjected to devastating blows," said Ukrainian presidential adviser Mykhaylo Podolyak.
He added that the shelling in Lutsk had shut down two central heating compounds.
"Russia's destructive war against civilians and major cities continues," he said.
Russian state media reported that the Ukrainian city of Volnovakha had been captured by Russian-backed separatist forces.
There is no independent confirmation of the capture of the city, which is a northern gateway to the besieged port city of Mariupol.