Ukraine has labelled Russia a "terrorist state" after Moscow's UK embassy tweeted that Ukrainian Azov battalion soldiers deserved a "humiliating death" by hanging.

The embassy tweet came after more than 50 Ukrainian prisoners of war (POWs) held by Russia were killed - Azov soldiers reportedly among them.

They died in an attack on Olenivka prison in Russian-held eastern Ukraine.

Ukraine and Russia blame each other for Friday's attack in the Donetsk region.

Twitter acknowledged that the post from the Russian embassy violated the social media company's "rules about hateful conduct" - but added that it may be in the public interest to keep it accessible.

Besides the Ukrainian government, many other Twitter users voiced outrage at the tweet.

It comes as Ukraine's President Volodymyr Zelensky issued a "mandatory evacuation" to all civilians still living in the region, warning of an intensification of fighting between Kyiv and Moscow's forces.

In a late night address, Mr Zelensky said "full support" will be offered to the hundreds of thousands of people still there.

The Olenivka prison camp is controlled by the Russian-backed self-proclaimed Donetsk People's Republic (DNR).

What happened there on Friday remains unclear. Unverified Russian video footage of the aftermath shows a tangle of wrecked bunk beds and badly charred bodies.

After the attack the Russian embassy in the UK tweeted that Azov "militants deserve execution, but death not by firing squad but by hanging, because they're not real soldiers. They deserve a humiliating death."

The tweet included a video clip showing a couple in a wrecked building, accusing Azov troops of having shelled their home. The embassy's call for execution repeats what the man in the video says.

Azov troops were forced to lay down weapons in May after fiercely defending for weeks

Azovstal, a giant steelworks in the south-eastern port of Mariupol, that was eventually captured by Russia.

The Azov Regiment was a nationalist group with far-right links when it was set up in 2014. It was later incorporated into Ukraine's National Guard.

Russia has long accused the regiment of being neo-Nazis and war criminals, as part of the Kremlin's propaganda campaign to justify its invasion of Ukraine on 24 February 2022.

Andriy Yermak, Ukrainian presidential chief of staff, wrote on Telegram that "Russia is a terrorist country".

"In the 21st Century, only savages and terrorists can say at a diplomatic level that people deserve to be executed by hanging for nothing. The RF [Russia] is a state sponsor of terrorism. What more proof do you need?" he said.

Ukraine has called for the United Nations and Red Cross to be allowed to investigate the deaths at Olenivka.

Ukraine says the site was targeted by Russia in an effort to destroy evidence of torture and killing. President Volodymyr Zelensky described the incident as a "deliberate Russian war crime".

Ukraine's foreign ministry spokesman Oleg Nikolenko tweeted: "There is no difference between Russian diplomats calling for execution of Ukrainian prisoners of war and Russian troops doing it in Olenivka.

"They are all accomplices in these war crimes and must be held accountable," DNR spokesman Daniil Bezsonov said the strike had killed 53 people and wounded 75. He called it a "direct hit on a barracks holding prisoners".

Russia's defence ministry said the strike had been carried out with US-made Himars artillery and it accused Ukraine of a "deliberately perpetrated" provocation. The ministry produced fragments of what it said were rockets fired by the Himars system.

As soon as it learned of the incident, the International Committee of the Red Cross (ICRC) asked for access to the Russian-run detention facility, and to surviving prisoners. So far, no access has been granted.

The ICRC's deputy head of delegation in Ukraine, Daniel Bunnskog, said granting access to POWs was an obligation under the Geneva Conventions.

Relatives of Ukrainian prisoners and their supporters were on the streets of Kyiv on Friday, voicing their anger. They have no doubt the prisoners were murdered by their Russian captors.

Russia accuses Ukraine of deliberately targeting the camp, using American-supplied rockets.

Western officials clearly don't believe it. Without directly blaming Russia, Britain's ambassador in Kyiv, Melinda Simmons, tweeted on Saturday that the incident at Olenivka looked like part of an increasingly worrying pattern of human rights abuses, and possible war crimes, committed in occupied eastern Ukraine.

US Secretary of State Anthony Blinken said Washington was committed to holding Russia accountable for atrocities committed by its forces.

Footage of the destruction within a hangar-like dormitory filled with burned or destroyed bunk beds appeared online on Friday morning. The footage came from Russian state TV channel

Russia 1. It then cuts to footage of destruction and bloodshed outside the building.

The BBC cannot verify whether the interior and exterior shots are at the same location.

The BBC's Reality Check team has however, confirmed that the shots of the outside of the building match Prison No. 120, near Olenivka.

The prison was empty before February 2022, and has been used exclusively for POWs and civilians who did not pass Russian filtration - a system where people are interrogated before it is decided where they will be sent.

Andriy Biletskyi, a founder of the Azov Regiment, said a number of the unit's soldiers were among those killed. (BBC)

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