Russia hit Ukraine with a barrage of missiles on Thursday, killing nine people and triggering a wave of power cuts, including at Europe's biggest nuclear power plant.
The UN nuclear agency's chief warned next time "luck will run out" in reference to the danger of repeated electricity outages at Ukraine's Zaporizhzhia facility.
Russia said the strikes were a response to a border incursion earlier this month and cast doubt over the extension of a vital UN-brokered grain deal, saying it would discuss its renewal with the UN on Monday.
The missiles fell across the country, causing the first civilian deaths in the western Lviv region, considered relatively safe and far from the front lines, in a long time as fighting raged in the town of Bakhmut in the east.
In Velyka Vilshanytsia, a small village outside the city of Lviv, shocked villagers searched through the rubble where Ukrainian officials said a Russian missile killed five people around 120 kilometers (75 miles) from the Polish border.
"We thought we were safe here," said Oksana Ostapenko, who lost her sister and two brothers-in-law when the missile struck.
For months Russia has pummelled key infrastructure in Ukraine with missiles and drones — disrupting water, heating and electricity supplies for millions of people.
Kyiv Mayor Vitali Klitschko said two people were wounded on Thursday and 40% of the population had been left without power for several hours.
On Prospekt Peremogy, in the west of Kyiv, three cars parked near a high-rise apartment building were charred and the ground was littered with shattered glass from windows, an AFP reporter said.
"I'd seen (the missile) flying towards my block of flats and when I got there I saw a big fire," said resident Igor Yezhov, 60, a car dealer.
"I was very scared."
A 34-year-old man died in the eastern city of Dnipro, local authorities said.
At least three others were killed when shelling hit a bus stop in the southern city of Kherson, said Andriy Yermak, Ukraine's presidential chief of staff.
The Russian missile strikes also left the country's second city of Kharkiv in the northeast without power, water or heating, the regional governor said.
Ukraine said the strikes cut off electricity supplies to the Zaporizhzhia nuclear power plant — in Russian-occupied territory — forcing it to operate on diesel generators before power was restored later on Thursday.
Ukraine said it was the sixth time that the facility had been disconnected from the electricity grid since Russian forces captured the plant last year.
The UN nuclear agency chief Rafael Grossi warned of the danger of the outages, saying "each time we are rolling a dice."
"If we allow this to continue time after time then one day our luck will run out," he warned.
The Russian army called the strikes "massive retaliation" in response to "terrorist actions organized by the Kyiv regime in the Bryansk region" and said that it had used Kinzhal hypersonic missiles.
It referred to claims that Ukrainian nationalists had crossed into the southern Bryansk region and killed two civilians, which Kyiv dismissed as a provocation.
Russia also called a vital UN-brokered grain deal — that ensures supplies to large parts of the developing world — "complicated" and not properly implemented.
It said it would discuss the renewal of the deal — which expires on March 18 — with the UN on Monday in Geneva.
The year-long Russian invasion of Ukraine has revived tensions in the pro-Russian separatist region of Transnistria in Moldova, where Moscow-backed authorities accused Ukraine of plotting a "terror attack."
Local authorities said the plot was "directed by Ukrainian security services, being prepared against a number of officials."
Ukraine denied the claims as a "provocation orchestrated by the Kremlin" while Moldova's government said it was investigating the claim but could not yet confirm it.
On the ground, Russia reported gains in the battle for the industrial city of Bakhmut, which has been the focus of months of fierce combat.
Russia's Wagner mercenary group, which has spearheaded the attack on Bakhmut, claimed on Wednesday to have captured the eastern part of the city.
NATO has warned that Bakhmut could fall to Russian forces "in the coming days" but said it would "not necessarily reflect any turning point in the war."
Poland said Thursday it had delivered Ukraine a further 10 Leopard tanks while allies would deliver more "very soon."