French forensic experts have arrived in Bucha near Kyiv to help Ukraine authorities establish what happened in the town where hundreds of bodies have been discovered since Russian forces withdrew.

Ukraine says the people were killed by Russian forces during their occupation of the area. Reuters has not been able to verify the number of people found dead in Bucha or the circumstances of their deaths.

The discovery of so many slain civilians in Bucha after the Russian withdrawal has provoked a global outcry. Moscow has denied responsibility and dismissed allegations its troops committed war crimes as fake news.

As the group from the French Gendarmerie's forensic science department looked on, workers in hazmat suits dug earth from a shallow grave and lifted out a heavy mass wrapped in an orange blanket.

Prosecutor General Iryna Venediktova said, citing witnesses, that the burnt body parts inside were those of a woman and her two children.

Venediktova said over the next couple of weeks the French experts would help the Ukrainian authorities establish what happened to the people in Bucha.

"We have now a lot of jobs unfortunately with war crimes," Venediktova said at the churchyard site, where locals hastily buried people who died during the town's occupation.

"When you see dead bodies here, from the other side, from the Russian Federation, they say it is all fake, all this is our theatre," Venediktova said.

Venediktova said the international experts would be able to see the situation for themselves. "They can see everything, they can see the situation here: real graves, real dead bodies, real bomb attacks. That's why for us this moment is very important."

Moscow, which has repeatedly denied targeting civilians since its Feb. 24 invasion of Ukraine, has called allegations that Russian forces executed civilians in Bucha while they occupied the town a "monstrous forgery" aimed at denigrating the Russian army.

Russian President Vladimir Putin said on Tuesday that images and footage of dead bodies strewn across the Ukrainian town of Bucha were fake.

Speaking at a televised news conference Putin compared Ukrainian allegations that Russian servicemen executed civilians in Bucha to what he said was the staging by the West of a chemical weapons attack in Syria aimed at incriminating Bashar al-Assad.

"It's the same kind of fake in Bucha," Putin said.

On Monday, the French authorities said the team, which includes experts on ballistics, explosives, and rapid DNA testing, would also be able to contribute what they find to an International Criminal Court investigation.

Local priest Andriy Halavin said their work would help prove to the world what happened to the people of Bucha, including those recently unearthed in his churchyard.

"They didn't just die from explosions, by chance, being in the wrong place at the wrong time, but they were deliberately shot," Halavin said.

"Some were in cars, driving, and they were shot. Some were walking on the street and they were shot."

"It's very important that the whole world sees the truth because Russian propaganda always tells stories and lies."

A satellite image shows buildings on fire in eastern Mariupol. Reuters.

More than 1,000 Ukraine marines surrender in key port of Mariupol, says Russia

More than 1,000 Ukrainian marines have surrendered in the besieged port of Mariupol, Russia's defence ministry said on Wednesday of Moscow's main target in the eastern Donbas region which it has yet to bring under its control.

If the Russians take the Azovstal industrial district, where the marines have been holed up, they would be in full control of Mariupol, which would allow Russia to reinforce a land corridor between separatist-held eastern areas and the Crimea region that it seized and annexed in 2014.

Surrounded by Russian troops for weeks, Mariupol would be the first major city to fall since Russia invaded Ukraine on Feb. 24, with the battle for the industrial heartland of Donbas likely to define the course of the war.

Ukraine's general staff said that Russian forces were proceeding with attacks on Azovstal and the port, but a defence ministry spokesman said he had no information about any surrender.

Reuters journalists accompanying Russian-backed separatists saw flames billowing from the Azovstal district on Tuesday.

On Monday, the 36th Marine Brigade said it was preparing for a final battle in Mariupol that would end in death or capture as its troops had run out of ammunition.

Thousands of people are believed to have been killed in Mariupol and Russia has been massing thousands of troops in the area for a new assault, Ukrainian President Volodymyr Zelenskiy said.

Ukraine says tens of thousands of civilians have been trapped inside the city with no way to bring in food or water, and accuses Russia of blocking aid convoys.

Russia's defence ministry said that 1,026 soldiers of Ukraine's 36th Marine Brigade surrendered, including 162 officers.

CHEMICAL WEAPONS WARNING

Chechen leader Ramzan Kadyrov, an ardent supporter of Russian President Vladimir Putin, urged remaining Ukrainians holed up in Azovstal to surrender.

"Within Azovstal at the moment there are about 200 wounded who cannot receive any medical assistance," Kadyrov said in a Telegram post. "For them and all the rest it would be better to end this pointless resistance and go home to their families."

Russian television showed pictures of what it said were marines giving themselves up at Illich Iron and Steel Works in Mariupol on Tuesday, many of them wounded.

It showed what it said were Ukrainian soldiers being marched down a road with their hands in the air. One of the soldiers was shown holding a Ukrainian passport.

Ukrainian Deputy Defence Minister Hanna Malyar has said there was a high risk of Russia using chemical weapons, echoing earlier warnings by Zelensky, who on Wednesday told the Estonian parliament by videolink Russia was using phosphorus bombs to terrorise civilians.

He did not provide evidence and Reuters has not been able to independently verify his assertion.

Chemical weapons production, use and stockpiling is banned under the 1997 Chemical Weapons Convention. Although condemned by human rights groups, white phosphorous is not banned.

Russia denies using chemical weapons, saying it had destroyed its last chemical stockpiles in 2017.

Moscow's incursion into Ukraine, the biggest attack on a European state since 1945, has seen more than 4.6 million people flee abroad, killed or wounded thousands and left Russia increasingly isolated on the world stage.

The Ukrainian prosecutor general's office said 191 children had been killed and 349 wounded since the start of the invasion.

The Kremlin says it launched a "special military operation" to demilitarise and "denazify" Ukraine. Kyiv and its Western allies reject that as a false pretext for an unprovoked attack.

Ukrainian President Volodymyr Zelensky speaks during an address where he says that Russian forces could use chemical weapons in Ukraine. Reuters.

FOUR PRESIDENTS VISITING KYIV

The presidents of Poland, Lithuania, Latvia and Estonia were on their way to Kyiv to meet Zelensky, an adviser to the Polish leader said on Wednesday.

The four join a growing number of European politicians to visit the Ukrainian capital since Russian forces were driven away from the country's north earlier this month.

U.S. President Joe Biden said for the first time that Moscow's invasion of Ukraine amounted to genocide, as Putin said Russia would "rhythmically and calmly" continue its operation and achieve its goals.

Russia has denied targeting civilians and has said Ukrainian and Western allegations of war crimes are fabricated.

Many towns Russia has retreated from in northern Ukraine were littered with the bodies of civilians killed in what Kyiv says was a campaign of murder, torture and rape.

Interfax Ukraine news agency on Wednesday quoted the Kyiv district police chief saying 720 bodies had been found in the region around the capital, with more than 200 people missing.

The General Headquarters of the Armed Forces of Ukraine said Russian forces were maintaining attacks on civilian infrastructure in the Kharkiv region in the northeast and the Zaporizhzhia region in central Ukraine.

At least seven people were killed and 22 wounded in Kharkiv over the past 24 hours, Governor Oleh Synegubov said. A 2-year-old boy was among those killed in the 53 artillery or rocket strikes Russian forces had carried out in the region, he said in an online post.

Reuters could not independently verify the information.

Russia denies targeting civilians. Putin on Tuesday used his first public comments on the conflict in more than a week to say Russia would "rhythmically and calmly" continue its operation, and expressed confidence his goals would be achieved.

Zelensky mocked Putin in an early morning address: "How could a plan that provides for the death of tens of thousands of their own soldiers in a little more than a month of war come about?"