Ukraine's foreign minister on Sunday accused Russian forces of carrying out a "massacre" in the town of Bucha, while U.S. Secretary of State Antony Blinken described images of dead bodies there as "a punch in the gut".
Russia's defence ministry denied the Ukrainian allegations, saying footage and photographs showing dead bodies in Bucha were "yet another provocation" by Kyiv.
After Ukraine said on Saturday its forces had reclaimed control of the whole Kyiv region, images of corpses in civilian clothes left behind by departing Russian troops prompted calls from officials in Ukraine and Europe for tougher sanctions on Russia.
The outrage in Ukraine and abroad added to pressure on Russian President Vladimir Putin because it increased the likelihood of further Western sanctions. Western nations have already hit Russia with deep economic sanctions as they seek to punish Moscow for the invasion, which began on Feb. 24.
"We are still gathering and looking for bodies, but the number has already gone into the hundreds," Foreign Minister Dmytro Kuleba said, according to his ministry.
"Dead bodies lie on the streets. They killed civilians while staying there and when they were leaving these villages and towns," Kuleba said.
He called on G7 nations to impose "devastating" new sanctions on Moscow and urged the International Criminal Court (ICC) to collect evidence of what he called Russian war crimes.
In Russia's first public comment on the allegations, the defence ministry in Moscow described photos and videos from Bucha as "another staged performance by the Kyiv regime for the Western media".
"During the time that Russian armed forces were in control of this settlement, not a single local resident suffered from any violent actions," it said.
Russia has previously denied targetting civilians and has rejected allegations of war crimes in what it calls a "special military operation" aimed at demilitarising and "denazifying" Ukraine.
On Saturday, Reuters saw bodies in a mass grave and still lying on the streets, while on Sunday the mayor of Bacha, Anatoliy Fedoruk, showed reporters two corpses with white cloth tied around their arms, one of which appeared to have been shot in the mouth.
The foreign ministers of Germany, France and Britain and the European Union's foreign policy chief were among those expressing outrage over the reports from Bucha. France's Jean-Yves Le Drian and Britain's Liz Truss both said their countries would support any war crimes investigation by the ICC.
ALLEGATIONS OF ATROCITIES
Oleksiy Arestovych, an aide to Ukrainian President Volodymyr Zelenskiy, said Ukrainian troops had found the bodies of women who had been raped and set alight as well as the bodies of local officials and children.
In Bucha, 37 km (23 miles) northwest of Kyiv city centre, town mayor Fedoruk said 300 residents had been killed during a month-long occupation by the Russian army.
Reuters could not immediately verify the allegations by Arestovych and Fedoruk.
"We can't help but see these images as a punch in the gut," Blinken said on CNN, adding that there needed to be accountability.
"We can't become numb to this. We can't normalize this. This is the reality of what's going on every single day as long as Russia's brutality against Ukraine continues," Blinken said.
Russia has pulled back forces that had threatened Kyiv from the north, saying it intends to focus on eastern Ukraine.
NATO Secretary-General Jens Stoltenberg, speaking to CNN on Sunday, said the pullback was not a real withdrawal but rather a repositioning that could be followed by further attacks.
FIGHTING IN SEVERAL AREAS
Fighting was reported on Sunday in several parts of Ukraine.
The governor of the eastern Donetsk region said shelling had continued throughout the night and day.
Missiles struck near the southern port of Odesa, with Russia saying it had destroyed an oil refinery used by the Ukrainian military. The Odesa city council said "critical infrastructure facilities" were hit.
Dmytro Lunin, governor of the central Poltava region, said the Kremenchug oil refinery, 350 kilometres (220 miles) northeast of Odesa, had been destroyed in a separate rocket attack on Saturday.
Two blasts were heard in the Russian city of Belgorod near the border with Ukraine on Sunday, two witnesses told Reuters, days after Russian authorities accused Ukrainian forces of striking a fuel depot there.
Evacuation efforts in the southeastern port of Mariupol and nearby Berdyansk were due to continue with a convoy of buses being prepared with help from the Red Cross.
The ICRC abandoned earlier attempts due to security concerns. Russia blamed the ICRC for the delays.
Mariupol is Russia's main target in Ukraine's southeastern region of Donbas, and tens of thousands of civilians there have been trapped for weeks with scant access to food and water.
There was little sign of a breakthrough in efforts to negotiate an end to the five-week war, although Russia's chief negotiator, Vladimir Medinsky, said talks were due to resume on Monday via videoconference.
Medinsky said that while Ukraine was showing more realism by agreeing to be neutral, renouncing nuclear weapons, not joining a military bloc and refusing to host military bases, there had been no progress on other key Russia demands.
"I repeat again and again: Russia's position on Crimea and Donbas remains UNCHANGED," he said on Telegram.
Russia annexed Crimea from Ukraine in 2014 and has recognised declarations of independence by the self-proclaimed republics of Luhansk and Donetsk in the Donbas area of eastern Ukraine which rose up against Kyiv's rule.
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