Officials reported that Russia launched 653 drones and 51 missiles overnight, most of which were shot down. One attack hit a railway hub in the city of Fastiv, outside Kyiv, destroying the main station building and damaging rolling stock.
President Volodymyr Zelensky said the attack was "military-wise pointless, and the Russians were unaware of this."
Earlier, US and Ukrainian negotiators had appealed to Russia to demonstrate a "serious commitment to long-term peace" after talks in Moscow yielded no results.
Moscow has stepped up attacks on Ukraine's energy sector and infrastructure in recent weeks.
On Saturday, Ukraine's Energy Ministry said Russian attacks targeted energy facilities in eight areas, causing blackouts. Meanwhile, the UN's nuclear watchdog said the Zaporizhzhia nuclear power plant briefly lost all external power overnight – the 11th time this has happened since Russia launched a large-scale attack on its neighbor.
The Russian Defense Ministry said it had launched a "major attack" in response to Ukrainian attacks on civilian targets.
Ukrainian Foreign Minister Andriy Tsibiha said, "Russia is ignoring any peace efforts and instead attacking vital civilian infrastructure."
He added, "This shows that any decision to strengthen Ukraine and increase pressure on Russia cannot be delayed. And especially not under the pretext of the peace process."
In Florida, a statement posted by US Special Envoy Steve Witkoff said that two days of talks with Ukraine's National Security Council Secretary Rustam Umarov were "constructive."
His statement, without providing details, said that Witkoff and Umarov "agreed on a framework for security arrangements" that could lead to such a deal and "discussed the deterrence capabilities necessary to maintain a lasting peace." The statement further stated that hopes of ending the war depended on Russia's willingness to "take steps to reduce tensions and stop the killing."
The talks, which also included US President Donald Trump's son-in-law, Jared Kushner, will continue for a third day on Saturday.
The Ukraine team at the Florida talks was briefed on a recent meeting between Witkoff, Trump's most senior foreign envoy, and Russian President Vladimir Putin.
Witkoff spent nearly five hours with Putin in Moscow on Tuesday, after which the Kremlin said there was "no agreement" on a draft US peace plan.
The Kremlin said Putin is ready to continue meeting with the Americans "as often as needed," but Ukraine and its allies in Europe have questioned the Russian leader's commitment to ending the war.
On Friday, Ukrainian President Volodymyr Zelensky said he wants "full information about what was said in Moscow and what other excuses Putin has used to prolong the war."
Kyiv has insisted on changes to the initial US peace plan, which was seen as beneficial to Moscow after its initial version was leaked to the media. The updated version has not been shared publicly.
Major issues of contention remain between the two sides, including security guarantees and territorial concessions for Ukraine after the war.
Russia currently controls about one-fifth of Ukraine, including a large part of the Donbas region in the east – made up of the Donetsk and Luhansk regions.
In an interview with India Today on Friday, Putin warned Ukrainian troops to completely withdraw from the region this week, saying that otherwise Russia would "liberate these [Donbas] areas by force."
Kyiv and its European allies believe that the most effective way to deter Russia from attacking again in the future would be to grant Ukraine NATO membership, or provide full security guarantees.
Russia is strongly opposing this, while Trump has repeatedly indicated that he has no intention of allowing Ukraine to join the military alliance. The Kremlin said on Wednesday that the possibility of Ukraine joining NATO was an "important question" discussed in Moscow.
Trump said the talks were "very good," but it was too early to say what would happen because "it takes two to tango."