Ukraine reported pushing back Russian forces in a counter-attack that could signal a shift in the momentum of the war and shut gas flows on a route through Russian-held territory, raising the spectre of an energy crisis in Europe.
Ukraine's armed forces' general staff said it had recaptured Pytomnyk, a village on the main highway north of the second-largest city of Kharkiv, about halfway to the Russian border.
"The occupying forces moved to the defence in order to slow down the pace of the offensive of our troops," it said. "The settlement of Pytomnyk ... was liberated."
Following days of advances north and east of Kharkiv, one Ukrainian military source said on condition of anonymity that Ukraine's forces were within just several kilometres of the Russian frontier by Wednesday morning.
Beforehand, Russian forces had been on the outskirts of Kharkiv, a city 40 km (25 miles) from the frontier.
Russia said on Thursday its forces hit two ammunition depots in the Chernihiv region of Ukraine. The defence ministry said Russia had destroyed a Ukrainian S-300 air defence missile system in the Kharkiv region and a radar station near Odesa.
One of Russian President Vladimir Putin's closest allies warned the West that the increasing military support given to Ukraine by the United States and its allies risked triggering a conflict between Russia and NATO.
The Russian military's failure to seize the Ukrainian capital was inevitable as in the preceding years they had never directly faced a powerful enemy, and they are not up to the job in Ukraine, said a former mercenary with the Kremlin-linked Wagner Group who fought alongside the Russian army.
Reports of battlefield developments could not be immediately verified by Reuters.
Ukraine's announcement on Tuesday that it would suspend the flow of gas through a transit point bringing Russian fuel to Europe does not present a gas supply issue, the European Commission said on Thursday.
Moscow has slapped sanctions on the owner of the Polish part of the Yamal pipeline that brings Russian gas to Europe, as well as the former German unit of the Russian gas producer Gazprom, whose subsidiaries service Europe's gas consumption.
NATO allies expect Finland and Sweden to apply to join the alliance in the coming days and will grant membership quickly, diplomats and officials said, as Russia's invasion of Ukraine forces a radical rethink of European security.
Sweden's government plans to submit an application to join NATO next week, following neighbour Finland in re-writing its post-World War Two security policy, Expressen newspaper reported on Thursday.
The U.N. Human Rights Council will decide on Thursday whether to launch an investigation into alleged abuses by Russian troops in the Kyiv area that Ukraine says amount to war crimes. Russia denies targeting civilians.
The near-constant crump of shellfire washed over the battered hamlet of Vilkhivka, testifying to fierce fighting beyond its wind-swept fields between Ukrainian troops pressing a counter-offensive and Russian forces that once occupied the area.
Villagers have only just begun filtering back to retrieve possessions from properties, salvaging what they can despite the peril from unexploded ordnance.
In epic detours via Russia, Ukrainians are skirting the war front to flee to the European Union.