President Volodymyr Zelenskiy has accused Russia of exploiting a US-backed energy truce to stockpile munitions, and using them to attack Ukraine with hundreds of drones and a record number of ballistic missiles a day before peace talks.
The overnight attack in the early hours of Tuesday knocked out heating in cities including the capital Kyiv during freezing temperatures as Ukrainian negotiators headed to Abu Dhabi for a second round of US-brokered trilateral talks set for Wednesday and Thursday.
"It was a deliberate attack against energy infrastructure, involving a record number of ballistic missiles," Zelenskiy wrote on X, a day after saying Moscow had largely observed the moratorium agreed by the two sides on energy facilities.
"The Russian army exploited the US proposal to briefly halt strikes - not to support diplomacy but to stockpile missiles."
Ukraine is under US pressure to agree to a peace deal while attacks by Russia on its energy system appear intended to freeze Ukrainians into submission during one of the coldest winters in years.
The first round of trilateral talks in late January brought no movement on territorial issues, with Moscow demanding Kyiv cede more land in east Ukraine, which it refuses to do.
Sharpening his tone from previous days, Zelenskiy said on Tuesday the work of Ukraine's negotiators would be "adjusted accordingly" after the attack, but offered no details.
Speaking to reporters in Kyiv at a press conference with NATO Secretary General Mark Rutte, he said Ukraine would approach Washington to discuss new consequences for Russia.
Ukrainian officials said Russia launched 450 drones and over 70 missiles in strikes that wounded at least 12 people and struck apartment blocks and energy infrastructure as temperatures hovered around -20 Celsius.
More than 1000 apartment buildings in Kyiv and nearly 270,000 residents in Ukraine's second city of Kharkiv remained without heating, officials said.
"The goal is obvious: to cause maximum destruction and leave the city without heat in severe cold," wrote Kharkiv Mayor Ihor Terekhov on Telegram, adding that a thermal plant in the city had been badly damaged.
Russia and Ukraine said last week they had halted strikes on each other's energy infrastructure, but they disagreed on the timeframe for the moratorium. The Kremlin said it expired on February 1. Kyiv said it should last until this Friday.
Much of Ukraine has been gripped by a new wave of bitter cold after what Ukrainian experts said was the coldest January in six years.
Families languish in frigid and darkened apartments during power outages and cuts to heating that last hours and days.
On Monday, Zelenskiy said Russia had not carried out any strikes on Ukrainian energy infrastructure in the past 24 hours, and that "de-escalation measures... are helping to build public trust" in the peace process.
Kyiv resident Natalia Hlobenko, 35, described how she rushed to cover her 11-year-old son just on Tuesday before an explosion sprayed her apartment with broken glass.
"Where is this ceasefire?" said a teary Hlobenko, bundled in her windowless apartment.
"Honestly, how much can we take?"
Zelenskiy has previously said Ukraine, which is struggling to stop grinding Russian battlefield advances, was ready for "substantive" talks. Moscow and Kyiv blame each other for the failure to agree a peace deal.
Territory remains the main sticking point, with Ukraine resisting Russia's demands that it cede the remaining 20 per cent of the eastern region of Donetsk that Moscow has been unable to conquer since its 2022 invasion.
Ukraine's lead negotiator said Ukrainian officials would first hold bilateral talks with US officials in Abu Dhabi to discuss US security guarantees for any peace deal and a post-war reconstruction package, and later hold a trilateral meeting involving Russian negotiators.
The talks follow US President Donald Trump's announcement of a trade deal with India cutting tariffs in exchange for India halting Russian oil purchases and lowering trade barriers.
