Russia said Tuesday it was carrying out "massive strikes" across the Ukrainian frontline and accused Kyiv's soldiers of abusing civilians in territories recaptured in a dramatic counter-offensive.
Moscow's retaliation came after it was forced to pull back troops from swathes of the northeast, particularly in the Kharkiv region, following Kyiv's lightning assault to wrest back terrain.
The territorial shifts marked one of Russia's biggest setbacks since its troops were repelled from Kyiv in the earliest days of the nearly seven-month-long war, yet Moscow signalled it was no closer to agreeing to a negotiated peace.
"Air, rocket and artillery forces are carrying out massive strikes on units of the Ukrainian armed forces in all operational directions," the Russian defence ministry said in its daily briefing on the conflict.
"High-precision" strikes have also been launched on Ukrainian positions around Sloviansk and Konstantinovka in the eastern Donetsk region, it added.
President Vladimir Putin's spokesman said that in the Kharkiv region, reports were emerging of "outrageous" treatment of civilians.
"There are a lot of punitive measures... people are being tortured, people are being mistreated and so on," Dmitry Peskov told journalists.
Russia's allegations came after Ukrainian authorities claimed to have found four bodies of civilians with "signs of torture" in the recaptured eastern village of Zaliznychne.
Moscow also pushed back on Tuesday against what it called growing "bias" at United Nations' human rights bodies, a day after a top UN official condemned Moscow's "intimidation" of people in Russia opposed to its war in Ukraine.
- 'Shift in momentum' -
Ukrainian forces launched their counter-offensive in early September, seemingly catching Russia's military off guard.
Images posted by the Ukrainian military showed crates of munitions and military hardware scattered across territory abandoned by Russian forces.
Around the northeastern town of Balakliya, AFP journalists saw evidence of fierce battles, with buildings destroyed or damaged and streets mostly deserted.
President Volodymyr Zelensky said Tuesday that Ukraine had completed "stabilization measures" in more than 4,000 square kilometres (1,500 square miles) of recaptured territory, and was working to do the same in a similarly sized area.
"The remnants of occupiers and sabotage groups are being discovered, collaborators are being detained, the entire security is being restored," he said in his evening address.
In the northeast, dozens of areas including the cities of Izyum, Kupiansk and Balakliya have been retaken, Ukraine said.
Ukrainian forces in the Kharkiv region have since September 6 reclaimed more than 300 settlements and areas home to around 150,000 people, said deputy foreign affairs minister Ganna Maliar.
US National Security Council spokesman John Kirby said Tuesday that Washington would soon provide another tranche in its multi-billion-dollar effort to supply arms to Ukraine.
Kirby said it is too early to say whether gains by Ukraine signal a turning point in the overall war.
"What you're seeing is certainly a shift in momentum by the Ukrainian armed forces," he said, but Zelensky should be the one to "determine and decide whether he feels militarily they've reached a turning point."
Despite the "dramatic events... it's war and war is unpredictable," Kirby added.
- Germany holds back -
Ukraine Defence Minister Oleksii Reznikov told French daily Le Monde in a Monday interview that the war has entered a new phase with the help of Western weapons.
Kyiv has nonetheless ramped up its calls for Western allies to rush more sophisticated weapons to help in its fight.
"Weapons, weapons, weapons have been on our agenda since spring. I am grateful to partners who have answered our call: Ukraine's battlefield successes are our shared ones," Foreign Minister Dmytro Kuleba said.
But Germany was once again under the spotlight for failing to deliver Leopard battle tanks that Kyiv is seeking.
"Not a single rational argument on why these weapons cannot be supplied, only abstract fears and excuses," said Kuleba, after Chancellor Olaf Scholz dodged a question on the issue on Monday, saying only that Germany would not "go-it-alone" on weapons deliveries.
In a phone call, the German leader urged Putin to "come to a diplomatic solution as quickly as possible, based on a ceasefire, a complete withdrawal of Russian forces and respect for the territorial integrity and sovereignty of the Ukraine".