Ukraine has accused Russian forces of committing war crimes and a “massacre” in Bucha, a town 18 miles north-west of the capital, Kyiv, after the bodies of unarmed Ukrainian civilians and mass graves were found on Sunday. Bodies of civilians – many with bound hands, close-range gunshot wounds and signs of torture – were found on the streets after Ukrainian troops reclaimed the town.

Ukrainian prosecutors said they had found 410 bodies in towns near Kyiv, and 140 bodies had been examined on Sunday. Russia denied allegations that its forces killed civilians as it retreated from war-torn areas of the country.

Satellite images from Bucha appear to show an approximately 45ft-long trench dug into the grounds of a church where a mass grave has been identified.

World leaders condemned the killings and called for independent investigations. The French president, Emmanuel Macron, the UN secretary general, António Guterres, the German chancellor, Olaf Scholz, the British prime minister, Boris Johnson, and the US ambassador to the UN, Linda Thomas-Greenfield, all publicly condemned Russia’s actions.

The US secretary of state, Antony Blinken, described the killings as “a punch to the gut” and joined western allies in vowing to document the atrocities to hold the perpetrators to account.

Russia described the situation in Bucha as a “provocation” by Ukraine intended to disrupt peace talks. The Kremlin’s foreign ministry said Russia was seeking a UN security council meeting on the matter. Its defence ministry described the photos and videos as “another staged performance by the Kyiv regime”. Dmitry Polyanskiy, Russia’s UN security council deputy representative, tweeted on Sunday: “In the light of heinous provocation of Ukrainian radicals in Bucha Russia requested a meeting of UN security council on Monday April 4.”

Ukraine’s president, Volodymyr Zelenskiy, condemned Russian forces as “murderers”, “torturers” and “rapists” after the killings came to light, describing the Kremlin-ordered attack on his country as amounting to genocide. “How did they also become butchers? … They killed deliberately and with pleasure,” he said in a national address late on Sunday. He vowed to investigate and prosecute all Russian “crimes” in Ukraine.

Ukraine’s foreign minister, Dymtro Kuleba, said Bucha was a “deliberate massacre” while speaking on Times Radio on Sunday. Describing Russia as “worse than Isis”, he said Russian forces were guilty of murder, torture, rape and looting. He also urged G7 countries to impose “devastating” sanctions immediately.

Zelenskiy criticised the west’s “policy of concessions to Russia” in the lead-up to the war. Describing Ukraine’s past pursuit of Nato membership, he said: “They thought that by refusing Ukraine, they would be able to appease Russia, to convince it to respect Ukraine and live normally next to us … I invite Mrs Merkel and Mr Sarkozy to visit Bucha and see what the policy of concessions to Russia has led to in 14 years. To see with their own eyes the tortured Ukrainian men and women.”

Russian forces continued their attacks on other Ukrainian cities. Seven people died and 34 were wounded after a residential area in Kharkiv was struck on Sunday, local prosecutors said.

At least 70% of Chernihiv has been destroyed by Russian forces, the city’s mayor said on Sunday. Vladyslav Atroshenko said the “consequences” of the attacks were severe and mirrored those of other badly damaged cities in Ukraine such as Bucha and Mariupol.

Russian forces are continuing to “consolidate and reorganise” their offensive in Donbas, while the capture of Mariupol is a “key objective” of the Russian invasion, UK’s Ministry of Defence said.

The Ukrainian military claims Russia has launched a “hidden mobilisation” of about 60,000 soldiers to replenish units lost in Ukraine, according to its latest operational report.

Russian missiles struck “critical infrastructure”, most likely a fuel depot, near Ukraine’s southern port of Odesa in the early hours of Sunday but there were no casualties, officials in the city said.

The European Union should consider a ban on gas imports from Russia, Germany’s defence minister, Christine Lambrecht, has said.

The huge scale of sexual violence endured by women and girls in Ukraine has begun to emerge as victims recount the abuse they have suffered at the hands of Russian soldiers.

The United Nations’ human rights office says there have been 3,455 civilian casualties since the war in Ukraine began. The figure includes more than 1,400 deaths and over 2,000 injured people, but the actual number is believed to be considerably higher, the agency said in recently published report.

Zelenskiy appeared in a video message at the Grammy awards, calling for viewers to “fill the silence with your music” and “tell the truth about the war” across social networks and on TV.