Ukrainian officials have said that Russia had launched a "massive" drone attack on its cities and infrastructure overnight, warning that Moscow could be escalating its strikes ahead of winter.
"Last night there were about 40 'Shaheds'. More than half of them were shot down," President Volodymyr Zelensky said in a post on social media.
Russia has used hundreds of Iranian-made self-detonating Shahed drones to attack targets across Ukraine since the start of the conflict.
Concerns are growing that Russia will step up missile and drone strikes in a bid to cripple Ukraine's energy infrastructure through the winter.
"We realise that with the approach of winter, Russian terrorists will try to do more damage," Mr Zelensky added. "We will respond to the enemy. Powerfully."
Russian drones were launched at ten regions ranging from Kharkiv and Zaporizhzhia on the front lines to Kyiv in the centre and Lviv in the west, he said.
Ukraine's air force said it had shot down 24 of the drones as well as a Russian missile.
There were no reported fatalities, though there was significant damage to residential buildings and a college in the northeastern city of Kharkiv.
Kharkiv Mayor Igor Terekhov also said a dormitory in the city housing internally displaced people had been hit.
Dozens of firefighters worked for hours to put out the blazes caused by the attacks.
Interior Minister Igor Klymenko described it as a "massive" attack, while presidential chief of staff Andriy Yermak warned Russia was "gradually increasing its air attacks on Ukraine".
In the western region of Lviv, Governor Maksym Kozytsky said Russian drone strikes had hit five critical infrastructure sites, without providing more details.
A Ukrainian military spokesperson said the drones could have been trying to identify the locations of Ukraine's air defence systems.
Russia tends to launch drones in small groups, an "obvious" feature of likely reconnaissance activity, Natalia Gumeniuk, spokesperson for Ukraine's Operational Command South told journalists Friday.
"As the winter period gets longer and the weather gets colder, the enemy may launch more massive attacks," she added.
Russia's defence ministry said overnight it had shot down two Ukrainian drones over Belgorod region, which borders Ukraine.
Separately, Ukraine said a 29-year-old man injured in an October 21 missile strike on a postal depot in the Kharkiv region had died, taking the death toll from the strike to eight.
Zelensky ponders idea of 2024 election
Meanwhile, Volodymyr Zelensky is weighing the pros and cons of a spring 2024 presidential vote, his foreign minister said, though there are major concerns over how to organise a free and fair vote during war with Russia.
After Russia invaded in February 2022, Ukraine declared martial law which prohibits elections.
But there have been some calls, including from US Republican Senator Lindsey Graham, for votes to proceed even if the war does not end, as evidence of democratic health.
"We are not closing this page. The president of Ukraine is considering and weighing the different pros and cons," said Dmytro Kuleba, adding that elections would bring unprecedented challenges.
Ukraine was scheduled to hold a parliamentary election in October and a presidential vote in March 2024.
Kuleba made his comment during an online appearance at the World Policy Conference in the United Arab Emirates when asked whether Ukraine would hold a presidential election in spring.
He pointed to problems of security risks and how to ensure votes for hundreds of thousands of soldiers, millions of Ukrainians abroad and those living under Russian occupation.
President Zelensky has said elections can take place if needed, but that parliament would have to change the law and foreign assistance would be needed to help foot the bill and find somewhere for millions to vote abroad.
He has said he wants to run for another term if an election happens. His ratings remain very high, although they have fallen slightly since the first year of war.
Russia controls nearly a fifth of Ukraine and about 6 million Ukrainians now live around Europe.
Political analysts and some opposition politicians have said it would be extremely difficult for Ukraine to guarantee a free, fair and safe electoral process as Russia continues to strike the country with drones and missiles.
Several major TV networks - vital platforms for election campaigning - are also transmitting a single wartime broadcast.
Opponents of holding a vote fear Russia would try to derail it while political jockeying would undermine national unity.
