After the withdrawal of Russian troops from the area around the Ukrainian capital Kiev, photos of people killed in the recaptured town of Bucha have prompted new outrage.
"What happened in Bucha and other suburbs of Kiev can only be described as genocide," Kiev Mayor Vitali Klitschko told the Sunday edition of Germany's mass-circulation Bild newspaper.
At the same time, he held Russia's President Vladimir Putin personally responsible. "These are cruel war crimes that Putin is responsible for there. Civilians shot with hands tied."
Ukrainian presidential adviser Mykhailo Podolyak shared a photo on the short message service Twitter showing men who had been shot. One of the men had his hands tied behind his back.
Numerous bodies had been found in Bucha after the Russian army withdrew. Bodies were also lying in the streets. According to the authorities, 280 people have now been buried in mass graves.
The authenticity could not be independently verified.
Another photo showed dead bodies on a street. "The hell of the 21st century," Podolyak commented.
Ukrainian Foreign Minister Dmytro Kuleba branded Russia worse than Islamic State in comments to Times Radio cited by Britain's Press Association (PA), and said it is possible its military actions could amount to genocide.
"Shocked by haunting images of atrocities committed by Russian army in Kyiv liberated region," EU Council President Charles Michel tweeted, using an alternative spelling for the Ukrainian capital.
He said the EU would help gather evidence to bring those responsible before international courts. At the same time, he announced further EU sanctions targeting Russia and support for Ukraine.
European Commission President Ursula von der Leyen wrote on Twitter that she was "appalled by reports of unspeakable horrors in areas from which Russia is withdrawing."
"An independent investigation is urgently needed," she wrote. "Perpetrators of war crimes will be held accountable."
The Russian Defence Ministry in Moscow did not comment on the accusations at first.
Elsewhere there were plans for yet another attempt to evacuate people from the besieged port city of Mariupol on Sunday.
"Seven buses will try to get closer to Mariupol," Deputy Prime Minister Iryna Vereshchuk announced on the Telegram news channel. These buses would be accompanied by representatives of the International Committee of the Red Cross.
According to estimates, there are still about 100,000 inhabitants in the embattled and now heavily damaged city. Several attempts had been made to reach Mariupol in recent days.
Russia accuses the Red Cross of having prepared the evacuation poorly. On Saturday, a convoy did not even reach the city of Berdyansk as a planned stopover, for unknown reasons and with a long delay, according to Moscow.
According to Vereshchuk, 17 buses were ready near Berdyansk on Sunday. Ten of them were destined for the inhabitants of Mariupol. If the buses did not get through, they were to wait in Berdyansk. In addition, it was possible to travel by private car from Mariupol to Zaporizhzhia to the north-west via another escape route.
Russian Major General Mikhail Mizintsev said earlier foreign nationals would be able to leave Mariupol and travel towards Berdyansk, while those in Berdyansk would be able to leave the area either by land via Crimea or through Ukrainian-controlled areas, Russian news agency TASS reported.
The foreign nationals concerned are largely crew members of freight ships that have been blocked at both ports since the war began.
Russia also said it had attacked targets near the Ukrainian port city of Odessa on the Black Sea.
Rockets were fired from ships and aircraft at an oil refinery and three fuel depots, the Defence Ministry announced in Moscow on Sunday. The city council of the metropolis with about 1 million inhabitants had previously reported fires in the city area.
According to Russian information, a total of 51 military facilities were hit overnight, including four command posts and two missile defence systems. This information could not be independently verified.
Since the beginning of the war on February 24, the Russian army claims to have destroyed a total of 125 Ukrainian aircraft, 88 helicopters, 383 drones, 221 missile defence systems as well as 1,903 tanks and other armoured vehicles.
Moscow claims that it only attacks military targets in its neighbouring country. Ukraine, on the other hand, accuses Russia of also shelling civilian infrastructure and residential areas.
Russia has dampened hopes Ukraine will soon hold a top-level meeting between Presidents Vladimir Putin and Volodymyr Zelneknsky to end the war.
There is still much to be done, Russian negotiator Vladimir Medinsky told the Interfax news agency on Sunday.
"I unfortunately do not share Arakhamia's optimism." Earlier, Ukraine's chief negotiator David Arakhamia had spoken on Ukrainian television of a possible meeting soon between the two leaders.
The drafts of the relevant documents had already progressed to the point where "direct talks between the two heads of state" were possible, Arakhamia said, adding that Ukraine had also already indicated concessions.
Russia's chief negotiator Medinsky, on the other hand, stressed that Russia's position on Crimea and the Donbass was "unchanged."
Moscow is demanding that Ukraine renounce NATO membership and recognize the breakaway eastern Ukrainian separatist regions in the Donbass as independent states and the Black Sea peninsula of Crimea, annexed in 2014, as part of Russia.
Ukrainian presidential adviser Olexiy Arestovych expects the war to end in "two to three weeks." Everything now depends on the outcome of the fighting in the south-east of the country, he said.
The Russian army no longer has any reserves, the adviser claimed, according to a report on the news site strana.news. There has been speculation for some time that Putin could end the war by the time of the celebrations marking the end of World War II. In Russia, this is on May 9.