Russia has intensified strikes on Ukraine, with the highest number of drones and missiles launched in a single night yet.
At least 12 people, including three children, were killed and dozens injured, Ukrainian officials said.
The attack was the second large-scale assault on the country in 48 hours, coming a day after the Ukrainian capital Kyiv suffered one of the heaviest assaults since the start of the Russian invasion.
Saturday's overnight strikes come as Russia ignores calls for a ceasefire.
Rescuers were working in more than 30 cities and villages after the "massive" strike, Ukrainian President Volodymyr Zelensky said in a statement on Sunday morning.
"Russia is dragging out this war and continues to kill every day," he said.
"The world may go on for a weekend, but the war continues, despite weekends and weekdays. This cannot be ignored."
Ukraine is again urging its allies to apply more pressure on Moscow to engage in a ceasefire.
"Without really strong pressure on the Russian leadership, this cruelty cannot be stopped," he added, calling for fresh sanctions.
Zelensky said "America's silence will only encourage Putin" - an apparent effort to exert pressure on US President Donald Trump who has said the Russian leader is interested in ending the war.
Putin launched a full-scale invasion of Ukraine in February 2022, and Moscow currently controls about 20% of Ukrainian territory.
This includes Crimea - Ukraine's southern peninsula annexed by Russia in 2014.
In terms of the numbers of drones and missiles launched, Saturday night was the highest yet.
Russia is able not only to just manufacture them at a faster rate, but they are also evolving. Shahed drones are now being packed with more explosives and improved technology to evade detection.
Ukraine's Air Force said that since 20:40 on Saturday local time (17:40 GMT), Russia had carried out strikes using 367 missiles of various types, unmanned aerial vehicles (UAVs) and drones.
The air force said it had shot down 45 cruise missiles and neutralised 266 UAVs, with most regions in Ukraine affected and hits recorded in 22 locations.
Deaths were reported in several regions.
Russia's defence ministry said it had inflicted damage on targets including military airfields, ammunition depots and electric warfare stations, claiming damage across 142 areas.
According to Ukraine's Minister of Internal Affairs, Ihor Klymenko, 13 regions were attacked, with more than 70 people injured, 80 residential buildings damaged, and 27 fires recorded.
He called it a "combined, ruthless strike aimed at civilians".
Of the 12 people killed, three were children aged eight, 12 and 17 in the Zhytomyr region, Ukraine's state emergencies service DSNS said.
Klymenko said they were from the same family and their parents were in hospital.
In the Kyiv region, four people were killed and 16 injured, including three children, DSNS said.
In Kyiv, local officials reported 11 injuries, multiple fires and damage to residential buildings, including a dormitory.
Hundreds of people headed to the city's deep metro stations for shelter. The din of drones filled the air, occasionally punctuated by the booms of air defences, or the moments of impact. Several fires were reported.
A BBC colleague messaged to say a block of flats had been destroyed, just a five minute drive from where she lived.
The strikes come as the capital marks its annual Kyiv Day holiday.
In Russia, the defence ministry said 110 Ukrainian drones were destroyed and intercepted over 12 Russian regions and the Crimea peninsula between midnight and 0700 local time.
Moscow Mayor Sergei Sobyanin reported that 12 drones heading towards the capital were shot down.
He added that emergency services crews were deployed to assess damage caused by falling drone debris.
In the Tula region, just south of Moscow, drone wreckage crashed in the courtyard of a residential building, smashing windows in a number of apartments, local governor Dmitriy Milyaev said.
No-one was injured, he added.
Sunday is also the third and final day of a major prisoner of war exchange between the two sides, and after this weekend, there is even less hope it will lead to further co-operation.
On Friday, Ukraine and Russia each handed over 390 soldiers and civilians in the biggest prisoner exchange since Russia launched its full-scale assault in February 2022.
On Saturday, Zelensky announced that another 307 Ukrainian prisoners had returned home as part of an exchange deal with the Kremlin.
And on Sunday, Ukraine and Russia each confirmed 303 of their soldiers had returned home - bringing the total over the three days to 1,000 prisoners each.
The swap follows the first face-to-face talks between the two sides in three years, which took place in Turkey.
Earlier this week, Trump and Putin had a two-hour phone call to discuss a US-proposed Ukraine ceasefire deal.
Trump said he believed the call had gone "very well", and added that Russia and Ukraine will "immediately start" negotiations toward a ceasefire and "an end to the war".
However, Putin has only said Russia would work with Ukraine to craft a "memorandum" on a "possible future peace", and has not accepted a 30-day ceasefire.
