Russian long-range strikes have killed at least 10 civilians and hurt 20 others in several areas of Ukraine, Ukraine’s presidential office said.
It comes as a senior Moscow official said the Kremlin’s forces are prepared for an expected Ukrainian counteroffensive in the coming weeks.
Five people died in Kostiantynivka, a town in eastern Ukraine’s Donetsk province, when a Russian missile hit an aid station.
Ukrainian authorities last year established hundreds of so-called “points of invincibility”, where residents hard-pressed by the war could warm up, charge their mobile phones and get snacks.
Local prosecutors said the Russians attacked Kostyantynivka with S-300 anti-aircraft missiles.
The civilians who died were refugees, according to Donetsk governor Pavlo Kyrylenko.
As the mostly artillery war of the recent winter months stretched into its second spring, Russian forces also used air-launched missiles, exploding drones and gliding bombs in their attacks on several regions early on Friday, Ukrainian air force spokesman Yurii Ihnat said.
Two civilians died and nine were wounded in the Sumy province town of Bilopillia by a nighttime rocket and artillery barrage and air strikes, the administration of the northeast region said.
In the southern Kherson region, which Ukrainian President Volodymyr Zelensky visited on Thursday, Russian shelling killed one person in the main city, also called Kherson, and killed another person and wounded four others in the town of Bilozerka.
On Wednesday, a Russian drone attack hit a secondary school and dormitories south of Kyiv, killing at least nine people.
Kyiv’s forces are poised to use the improved spring weather and arrival of modern weapons, including tanks, supplied by its western allies to launch a counteroffensive aimed at dislodging Russian troops from occupied areas of Ukraine.
But Dmitry Medvedev, Russia’s former president and now the deputy head of Russia’s Security Council chaired by President Vladimir Putin, said the Russian military is ready to repel a counterattack.
“Our general staff is assessing all that,” Mr Medvedev said.
He also said a Ukrainian attempt to seize Crimea, which Russia annexed in 2014, could trigger a nuclear response from Moscow.
“An attempt to split part of the state away means an encroachment at the very existence of the state,” he said.
“Quite obviously, it warrants the use of any weapons. I hope our ‘friends’ across the ocean realise that.”
Though known for his bombastic pronouncements, Mr Medvedev’s warning stems from the Russian security doctrine envisaging the use of nuclear weapons in response to a nuclear attack or an attack with conventional weapons that threatens “the very existence of the Russian state”.
Mr Medvedev also said western experts operating weapons, such as the US-made Patriot air defence missile systems supplied to Ukraine, would be legitimate targets for the Russian military.
Ukrainian soldiers have received training in the US, although Russian officials have frequently claimed foreign instructors are present in Ukraine.
“If Patriot or other weapons are delivered to the territory of Ukraine along with foreign experts, they certainly make legitimate targets, which must be destroyed,” Mr Medvedev told reporters in video clips he posted on his messaging app channel.
“They are combatants, they are the enemies of our state and they must be destroyed.”
“They must understand that as soon as an American or a Polish soldier shows up there, he must be killed,” he added.
The Kremlin’s goal is to “create a sanitary cordon” of up to 60 miles around Russian-held areas so short and mid-range weapons cannot strike them, according to Mr Medvedev.
Moscow may even set its sights on grabbing a bigger chunk of Ukrainian territory, stretching all the way to the border with Poland, he added.