Russia and Ukraine have accused each other of violating a new agreement to refrain from attacks on energy targets hours after it was agreed by US President Donald Trump and Russian President Vladimir Putin.
But a prisoner swap touted as a confidence-building step went ahead, and Trump followed Tuesday's phone call with Putin with a call on Wednesday with Ukraine's President Volodymyr Zelenskiy, saying afterwards that "we are very much on track".
Trump said his "very good telephone call" with Zelenskiy lasted an hour, their first conversation since an Oval Office meeting descended into a public row on February 28.
The discussion followed Tuesday's call with Putin and aimed "to align both Russia and Ukraine in terms of their requests and needs," Trump posted on social media.
Putin had agreed to pause attacks on energy infrastructure, a proposal Zelenskiy accepted.
Even that narrow pause appeared in doubt on Wednesday, however, with Russia saying Ukraine hit an oil depot in southern Russia while Ukraine said Russia had struck hospitals and homes and also knocked out power to some of its railways.
Still, the two sides announced they had carried out a swap of prisoners, each releasing 175 troops in a deal facilitated by the United Arab Emirates.
Russia said it also freed an additional 22 wounded Ukrainians as a goodwill gesture.
Zelenskiy said on Wednesday that the continued attacks showed Russia's words did not match its actions, and that Russia was not ready for peace.
He said the United States should be put in charge of monitoring any ceasefire.
"If the Russians will not strike our facilities then we will definitely not strike theirs," he said at a briefing in Helsinki alongside the president of Finland.
The Kremlin said it had called off planned attacks on Ukraine's energy infrastructure, including by shooting down seven of Russia's own drones heading towards Ukraine.
It accused Ukraine of failing to call off its own attacks in what it called an attempt to sabotage the agreement.
Attacks on energy infrastructure have been a major part of the war's effect far from the front lines.
For most of the past three years, Russian forces have relentlessly attacked Ukraine's power grid, arguing that civilian infrastructure is a legitimate target because it facilitates Ukrainian war-fighting capabilities.
Ukrainian officials say such attacks have subsided in recent months, with backup power generators that once crowded the streets of Kyiv becoming less prominent since late 2024.
For its part, Ukraine has steadily developed capabilities to mount long-range attacks into Russia, frequently using drones to target distant oil and gas sites which it says provide fuel for Russia's troops and income to fund the war.
In the attacks overnight, Ukrainian regional authorities said Russian drones damaged two hospitals in the northeastern Sumy region, causing no injuries but forcing patients and staff to be relocated.
Near Kyiv, a 60-year-old man was injured and air strikes hit homes and businesses in the Bucha district north of the capital.
Attacks had damaged power systems for the railways in Dnipropetrovsk in the south on Wednesday, the railway said.
Authorities in the southern Russian region of Krasnodar said a Ukrainian drone attack caused a fire at an oil depot near the village of Kavkazskaya.
No one was injured in the fire, which had spread across 3700 sq metres as of 4pm Moscow time.
The depot is a rail terminal for Russian oil supplies to a pipeline linking Kazakhstan to the Black Sea.
A representative of the Caspian Pipeline Consortium operator said oil flows were stable; two industry sources said the attack could reduce Russian supplies to the pipeline.
