Moscow has stepped up a winter campaign against Ukraine's battered energy system while grinding forward on the battlefield, as Kyiv faces US pressure to secure peace after nearly four years of war, amid scant signs the Kremlin wants to stop fighting.
Drone and missile strikes killed four people on Tuesday - three in the southeastern city of Zaporizhzhia and one in the Kyiv region surrounding the capital. Other regions in the east, south and north of Ukraine also came under attack.
The attack was Russia's second this month on the Ukrainian capital. Tens of thousands of emergency workers have been toiling round the clock to restore power and heating, with overnight temperatures dipping to minus 13C.
"In Kyiv alone, as of this evening, more than one million households remain without power," President Volodymyr Zelenskiy said in his nightly video address.
"And a significant number of buildings have no heating, more than 4000 apartment buildings."
The president said he wanted his government to provide an "action and decision plan" on stabilising services by Wednesday.
Deputy Prime Minister Oleksiy Kuleba said 68 repair brigades had been deployed in Kyiv. More than 1400 emergency stations enabled residents to keep warm and charge electronic devices.
The United Nations' atomic watchdog said several substations critical for nuclear safety were affected by the attack, while power lines to some other nuclear plants were impacted. Ukraine gets well over half of its electricity from nuclear power.
The Chernobyl plant lost all off-site power on Tuesday, the International Atomic Energy Agency added. Kyiv later said the plant had been reconnected.
Ukrainian officials had warned in recent days that Moscow would target nuclear-related facilities.
"While Russian officials speak about the 'importance' of power lines, their forces deliberately strike substations, directly endangering nuclear safety," said Foreign Minister Andrii Sybiha.
Grid operator Ukrenergo said Russia's attack, which Ukraine said had included more than 330 drones and nearly three dozen missiles, targeted both power generation and distribution.
Authorities in the northern region of Chernihiv bordering Russia said 87 per cent of the population was without power.
Russia said it had attacked military-industrial, energy and transport targets in support of the army.
Tuesday's strikes followed a new round of peace talks at the weekend between US and Ukrainian officials in a US-backed diplomatic push for which Russia has shown little enthusiasm.
In the Swiss resort of Davos, where the World Economic Forum meetings are taking place, envoys for US President Donald Trump and Russian President Vladimir Putin said their meeting on a possible peace deal to end the war had been "very positive" and "constructive".
Zelenskiy urged the US to pile more pressure on Moscow, saying it had "not yet had the strength" to stop Russia.
"Can America do more? It can, and we really want this, and we believe that the Americans are capable of doing this," he told reporters in a WhatsApp media chat.
Zelenskiy said some of the Russian missiles fired on Tuesday had been produced this year and called for tougher sanctions on Moscow to curb its military production.
He said he was ready to travel to Davos if Washington was ready to sign documents on security guarantees for Ukraine and a post-war prosperity plan.
The power and heating cuts have forced Kyiv residents to bundle up inside their homes and improvise ways to stay warm, such as heating bricks or pitching tents indoors.
