Ukraine’s President Volodymyr Zelensky accused Russia of committing a “war crime” after a night of intense shelling killed three.
A guided bomb hit a blood transfusion centre in Kupiansk, Kharkiv, late on Saturday night, leaving two dead and four injured.
About 70 attack drones and missiles rained down on Ukraine overnight, including on a Ukrainian airbase thought to hold British-supplied Storm Shadow missiles.
Mr Zelensky shared an image of the transfusion centre on fire on social media.
Alongside it he wrote: “This war crime alone says everything about Russian aggression.
“Defeating terrorists is a matter of honour for everyone who values life.”
A woman in her eighties was also killed, by Ukrainian shelling in Russian-held Donetsk, Russian-appointed mayor Alexey Kulemzin said.
Kyiv officials said Russia’s bombardment of attack drones and air and sea missiles included cruise missiles launched from aircraft over the Caspian Sea and Iranian-made Shahed-136/131 strike unmanned aerial vehicles (UAVs).
Three waves of attacks using advanced Russian Dagger missiles and Iranian drones and missiles caused explosions in the vicinity of Starokonstantinov air base in Ukraine’s Khmelnytskyi region, Russian state-owned Rossiyskaya Gazeta reported.
The scale of the damage was unclear, but Russian sources claimed the base was used by Ukrainian Su-24 warplanes to fire British Storm Shadows and French version SCALP-EGs at Russian-held territory.
On Ukraine’s Day of Air Force, Russian reports say other air bases were attacked.
Russia’s Flightbomber Telegram channel said: “Particular attention was paid to Ukrainian airfields. so much that the remnants of their aviation had to hastily rush to the west at night.
“The Russian Air Force congratulated the Ukrainian Air Force on Aviation Day, so to speak.”
In Russia, a drone was shot down in Moscow airspace, briefly shutting down the city’s Vnukovo airport, nine miles southwest of the capital.
The Russian defence ministry said the drone was destroyed by air defence systems in the Podolsk region of the Moscow suburbs.
It is the fourth drone attack into Russia’s airspace in the last month. Flights were last halted at the airport on July 30 when two drones crashed into the Moscow city business district after being jammed by Russian air defences.
Elsewhere a 55-year-old man was hospitalised after a missile struck houses and farm buildings in Ukraine’s eastern Kupyan region. The attack also started a forest fire nearby.
Another person was injured when Russian missiles hit buildings and sparked a warehouse fire in the Khmelnytsky region, local military officials said.
Ukrainian shelling also started a fire and caused the roof to collapse at the M. Tugan-Baranovsky University of Economics and Trade in the Russian-held Donetsk, Russia said.
Russia had promised retaliation on Saturday after it claimed Ukrainian drones hit a Russian tanker in the Black Sea near Crimea.