"While everyone is discussing points of peace plans, Russia continues to pursue its 'war plan' of two points: to kill and destroy," Ukraine's foreign minister, Andrii Sybiha, wrote on Saturday morning as Kyiv residents surveyed the damage after a heavy night of explosions that mostly targeted the capital.
President Volodymyr Zelenskiy said Russia had launched around 36 missiles and nearly 600 drones in the overnight attack.
Ukraine's State Emergency Services said two people died in the overnight attack in Kyiv and 38 were injured.
Regional officials and police said one person had died in the region surrounding the capital, two in southeastern Dnipropetrovsk region and one in a midday attack in Kherson region in the south.
Moscow has conducted regular large-scale bombardments of Ukraine's power infrastructure since 2022, but the latest campaign this northern autumn has pushed Ukrainian cities including Kyiv into a torrid situation, with many households only getting eight hours of power on some of the worst days of blackouts.
The deafening roar of generators and the stench of diesel fumes now fill the capital's avenues, and people use torches at night as streetlights are often out.
Ukraine's largest private power producer, DTEK, said 420,000 customers had had their electricity restored in Kyiv, with smaller numbers still to be reconnected. Five other regions were also affected.
Russia's Defence Ministry said Moscow had launched a "massive" overnight strike on Ukrainian military-industrial and energy facilities in response to what it called "terrorist attacks".
Ukraine has been negotiating with the United States on the terms of a peace agreement that Washington is seeking to broker between Kyiv and Moscow to end Russia's nearly four-year-old war.
Zelenskiy said on Saturday that a delegation headed by Security Council Secretary Rustem Umerov was on its way to the United States to continue talks.
US Secretary of State Marco Rubio, special envoy Steve Witkoff and US President Donald Trump's son-in-law Jared Kushner will meet the Ukrainian officials on Sunday in Florida, a senior US official told Reuters.
Kyiv and its European allies say they want peace but pushed back against some of the original terms pushed by the US, with Ukraine unwilling to withdraw from land it currently holds and resisting any restriction on its future ability to join alliances.
In neighbouring Moldova, officials said Russian drones had entered the country's airspace, posing a threat to aviation, in the third such incident in nine days.
