Russia launched more than 700 drones and missiles at Ukraine in multiple waves overnight, killing at least 18 people in what local officials said was the deadliest attack in months.
Officials said nine people had been killed in the southern port city of Odesa, five in the central city of Dnipro, and four - including a child - in the capital, Kyiv.
In Russia, two people - including a child - were killed in a Ukrainian drone attack in the southern Krasnodar region, Moscow said.
This comes after a brief ceasefire took place over Orthodox Easter last weekend - though both sides accused one another of hundreds of violations.
Russia launched a full-scale invasion of Ukraine in February 2022.
In Kyiv, warning sirens jolted people awake at 02:30 local time on Thursday (23:30 GMT on Wednesday), followed soon after by the first explosions.
Images posted online by eyewitnesses show bright orange fires and huge plumes of black smoke in central areas of the city. In one video, a drone was filmed slamming straight into the side of an apartment block.
Kyiv Mayor Vitali Klitschko wrote on Telegram that a 12-year-old boy was among four people killed. Another 45 people were injured.
The mayor added that rescuers had pulled a mother and child from the ruins of a 16-storey residential building that collapsed in the city's central Podil district.
Four emergency medical workers were among those injured in the north of the capital.
In Dnipro, regional head Oleksandr Ganzha stated that four people were killed and dozens injured in the Russian attack - before the city's Mayor Borys Filatov reported another body had been found.
In the northeast city of Kharkiv, a drone strike injured a 77-year-old woman and a 66-year-old man, an official said.
Two cities in the south, Mykolaiv and Kherson, have been left without power, according to local officials.
Ukraine's air force stated that Russia had launched 659 drones and 44 cruise and ballistic missiles in the prior 24 hours.
The military reported that 636 drones and 31 missiles had been shot down - but there had been direct hits in 26 locations.
Ukrainian President Volodymyr Zelensky condemned the attack, writing on X that it proved that US and European sanctions against Russia should not be weakened. He emphasized the need for robust responses to the violence and called for peace efforts.
Earlier in the week, Zelensky warned of a critical shortage of Patriot air defense missiles amid the escalating conflict.
Ukrainian Foreign Minister Andrii Sybiha labeled the latest Russian assault a 'war crime' and urged allies to intensify support for Ukraine.
As global tensions rise, both countries face increasing pressure as the war continues into its fifth year.
