At least three people, including a four-year-old child, have been killed following a "massive" Russian strike across Ukraine, Ukrainian President Volodymyr Zelensky said.
"This Russian strike sends an extremely clear signal about Russia's priorities. An attack was carried out essentially in the midst of negotiations aimed at ending this war," he said in a post on the Telegram messaging app.
Mr Zelensky urged Ukraine's Western partners to increase pressure on Moscow.
Several Ukrainian regions suffered power cuts in frigid winter weather as a result of the attack.
Neighbouring Poland scrambled jets to protect its airspace.
"Russia once again is attacking our energy infrastructure. As a result, emergency power outages have been introduced in a number of Ukrainian regions," the country's energy ministry said on Telegram.
Fires broke out in several regions as a result of the "massive missile and drone attack", Ukraine's power operator Ukrenergo said, as temperatures dipped towards freezing in most of the country.
One person was killed in the western region of Khmelnytsky and another was killed in Kyiv, local authorities said.
Several people, including children, were wounded in a number of regions, according to local authorities.
Russia has intensified its strikes on the southern Ukrainian port city of Odesa over the past several days in what Ukrainian authorities say is an attempt to completely destroy maritime logistics.
Fresh strikes sparked fires but did not result in injuries in the Black Sea city, emergency services said.
Russian strikes on the Black Sea regions have intensified, hitting bridges, ports and cutting electricity and heating to thousands in the middle of winter.
Russian strike could collapse Chernobyl shelter: plant director
The Russian strike could collapse the internal radiation shelter at the defunct Chernobyl nuclear power station in Ukraine, the plant's director has said.
Kyiv has accused Russia of repeatedly targeting the facility, the site of a 1986 meltdown that is still the world's worst ever nuclear disaster, since Moscow invaded in February 2022.
A hit earlier this year punched a hole in the outer radiation shell, triggering a warning from the International Atomic Energy Agency (IAEA) that it had "lost its primary safety functions".
In an interview with AFP, plant director Sergiy Tarakanov said fully restoring that shelter could take three to four years, and warned that another Russian hit could see the inner shell collapse.
"If a missile or drone hits it directly, or even falls somewhere nearby, for example, an Iskander, God forbid, it will cause a mini-earthquake in the area," Mr Tarakanov said.
The latest strikes followed weekend negotiations that the United States held in Miami with Russian and Ukrainian delegations as part of its effort to end the war that began when Moscow sent troops into its neighbour in February 2022.
"Slow progress is being observed," state media reported Russian deputy foreign minister Sergei Ryabkov as saying, after both Russia and Ukraine sent negotiators to the Florida city for separate talks with US President Donald Trump's envoys Steve Witkoff and Jared Kushner.
Mr Witkoff had hailed "constructive" discussions with both sides, but there were no signs of a breakthrough.
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Mr Zelensky has said initial drafts of US proposals for a peace deal between Ukraine and Russia meet many of Kyiv's demands.
But he suggested that neither side in the almost four-year war is likely to get everything it wants in talks on reaching a settlement.
"Overall, it looks quite solid at this stage," the Ukrainian leader said of recent talks with US officials who are trying to steer the neighbouring countries toward compromises.
"There are some things we are probably not ready for, and I’m sure there are things the Russians are not ready for either," Mr Zelensky told reporters in Kyiv.
US President Donald Trump has for months been pushing for a peace agreement.
However, the negotiations have run into sharply conflicting demands from Moscow and Kyiv.
But Mr Witkoff said on Sunday he held "productive and constructive" talks in Florida with Ukrainian and European representatives.
"We are talking. It’s going OK," Mr Trump said while on holiday at his Mar-a-Lago estate in Florida.
Asked if he planned to speak to Mr Zelensky or Russian President Vladimir Putin, Mr Trump did not say, offering only of the fighting, "I’d like to see it stopped".
Mr Zelensky said that "nearly 90%" of Ukraine’s demands have been incorporated into the draft agreements.
The backbone of the proposed deal is a 20-point plan, he said.
Read more: Latest Ukraine stories
There is also a framework document on security guarantees between Ukraine, European countries, and the US, as well as a separate document on bilateral security guarantees granted to Ukraine by the US.
Several provisions are being discussed, according to Mr Zelensky.
They include the Ukrainian army remaining at a peacetime level of 800,000; membership in the European Union; and European forces, under the leadership of France and the UK and with a "backstop" from Washington, ensuring "Ukraine’s security in the air, on land, and at sea".
"Some key countries will provide presence in these domains; others will contribute to energy security, finance, bomb shelters, and so on," the Ukrainian president said.
Ukraine is arguing that this bilateral document should be reviewed by the US congress, with some details and annexes kept classified, Mr Zelensky said.
The US team is now in talks with Russian envoys, and Washington has asked that no details be released, he added.
Additional reporting: PA
