High-resolution satellite imagery has shown that bodies have been lying in the open for weeks in the Ukrainian city of Bucha, as Russia denies its soldiers had committed war crimes.

Russia’s UN Ambassador, Vassily Nebenzia, insisted at a news conference that during the time that Bucha was under Russian control “not a single local person has suffered from any violent action”.

But satellite imagery from commercial provider Maxar Technologies, first reported by the New York Times, proved the bodies had been there for weeks.

Western and Ukrainian leaders have accused Russia of war crimes before, and the International Criminal Court’s prosecutor has already opened an investigation.

But the latest reports ratcheted up the condemnation.

US President Joe Biden called for a war crimes trial against Russian leader Vladimir Putin and said he will seek more sanctions after the reported atrocities in Ukraine.

“You saw what happened in Bucha,” Mr Biden said, describing Mr Putin as a “war criminal”.

German Foreign Minister Annalena Baerbock said photographs from Bucha show the “unbelievable brutality of the Russian leadership and those who follow its propaganda”.

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French President Emmanuel Macron said there is “clear evidence of war crimes” in Bucha that demand new punitive measures.

“I’m in favour of a new round of sanctions and in particular on coal and gasoline – we need to act,” Mr Macron said on France-Inter radio.

Although united in outrage, the European allies appeared split on how to respond.

While Poland urged Europe to quickly wean itself off Russian energy, Germany said it would stick with a gradual approach of phasing out coal and oil imports over the next few months.

Russia had withdrawn many of its forces from the capital area after being thwarted in its bid to swiftly capture Kyiv.

It has instead poured troops and mercenaries into the country’s east in a stepped-up bid to gain control of the Donbas, the largely Russian-speaking industrial region that includes the besieged southern port city of Mariupol, which has seen some of the heaviest fighting and worst suffering of the war.

About two-thirds of the Russian troops around Kyiv have left and are either in Belarus or on their way there, probably getting more supplies and reinforcements, said a senior US defence official.

More than 1,500 civilians were able to escape Mariupol on Monday, using the dwindling number of private vehicles available to get out, Ukrainian Deputy Prime Minister Iryna Vereshchuk said.

But, amid the fighting, a Red Cross-accompanied convoy of buses that has been prevented for days on end from in a bid to delivering supplies and evacuating residents was again unable to get into the city, Ms Vereshchuk said.

Meanwhile, the Ukrainian military said Russian forces were preparing for an offensive in the south-east of Ukraine.

Russian forces are focused on seizing the cities of Popasna and Rubizhne in the Donetsk and Luhansk regions and the Black Sea port of Mariupol, the general staff said on its Facebook page. Donetsk and Luhansk are controlled by Russian-backed separatists and recognised by Moscow as independent.

Ukraine says a civilian ship is sinking in the port of Mariupol after Russian forces fired on it.

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The Ukrainian Interior Ministry said the ship was struck during “shelling from the sea” by Russia, causing a fire in the engine room. The crew was rescued, including one injured crew member, it added.

The ministry said the ship was flying the flag of the Dominican Republic and posted a picture of a cargo vessel. It did not specify how many people were on board or the nationalities of the crew members.

Russian forces have been bombarding Mariupol for weeks as they try to gain control of Ukraine’s south-eastern coastline.

The UN migration agency estimates more than 11 million people have fled their homes in Ukraine since Russia’s invasion.

The International Organization for Migration, in its first full assessment in three weeks, reported that more than 7.1 million had been displaced within Ukraine as of April 1. This comes on top of more than four million who have fled abroad, reported by the UN refugee agency.

The IOM said more than 2.9 million others are actively considering “leaving their place of habitual residence due to war”.

The general staff said access to Kharkiv in the east, Ukraine’s second-largest city, was blocked. “The enemy is regrouping troops and concentrating its efforts on preparing an offensive operation in the east of our country,” the statement said.

“The goal is to establish full control over the territory of Donetsk and Luhansk regions.”

Ms Vereshchuk said seven humanitarian corridors opened yesterday, including from Mariupol and Russian-controlled Berdyansk.

Corridors will also be open from the city of Tokmak in the Zaporizhzhia region and the cities of Severodonetsk, Lysychansk, Popasna and Hirske in the Luhansk region.

Ms Vereshchuk said in post on Telegram that the Russian troops “don’t allow anyone to enter Mariupol,” and that the Russians “blocked the representatives of the International Committee of the Red Cross” in the settlement of Manhush just west of Mariupol.

She said that, after negotiations, the Red Cross representatives “were released at night and sent to Zaporizhzhia”.