Russia and Ukraine both launch investigations into attack that killed at least 40 Ukrainian PoWs; Ukraine says it is ready to resume grain exports from ports

• Russia-Ukraine war: see all our coverage

Russia and Ukraine have both launched criminal investigations into strikes that have reportedly killed at least 40 Ukrainian prisoners of war who were held at a pre-trial detention centre in the village of Olenivka, after both countries blamed the other side for the attack.

Ukraine’s foreign minister, Dmytro Kuleba, has accused Russia of a “petrifying war crime” over the killings and called on world leaders to “recognise Russia as a terrorist state”.

Ukraine has said it is ready for grain exports to leave its ports again but is waiting for the go-ahead from the United Nations, which it hoped it would receive later on Friday.

Horrific video has emerged that appears to show a Russian soldier castrating a Ukrainian prisoner, who other reports suggest was subsequently murdered. The footage, reviewed by the Guardian, was originally posted on pro-Russian Telegram channels. Aric Toler at investigative outlet Bellingcat, suggested that the video – featuring a Russian soldier, wearing a distinctive black wide-brimmed hat, approaching another figure who has his hands bound and is lying face down with the back of his trousers cut away – appeared to be authentic .

At least five people have been killed and seven injured in a strike on a bus stop in the city of Mykolaiv, according to the regional governor, Vitaliy Kim. Graphic images from the scene show the street littered with bodies.

Vladimir Putin’s press secretary, Dmitry Peskov, said on Friday that Russia staunchly supported China’s sovereignty and territorial integrity, after the Chinese president, Xi Jinping, warned the US president, Joe Biden, against “playing with fire” over Taiwan in a phone call on Thursday.

Germany’s economy minister said on Friday that putting the Nord Stream 2 gas pipeline into operation was not an option as this would only play into the hands of the Russian president, Vladimir Putin. There is growing anger in Germany over soaring energy prices.

Aleksandr Viktorovich Ionov, a Russian operative who was subjected to US sanctions on Friday, has been charged with using political groups in the US to advance pro-Russia propaganda, including during the invasion of Ukraine earlier this year.

The US treasury department said on Friday it had imposed sanctions on another individual alongside Ionov, as well as on four entities that support the Kremlin’s global malign influence and election interference operations, including in the US and Ukraine.

Belarus recalled its UK ambassador on Friday in response to what it called “hostile and unfriendly” actions by London.

North Macedonia plans to donate an unspecified number of Soviet-era tanks to Ukraine as it seeks to modernise its own military to meet Nato standards, its defence ministry said on Friday.

Germany would deliver 16 Biber bridge-layer tanks to Ukrainian forces, the German defence ministry said.

A Ukrainian court on Friday reduced to 15 years a life sentence handed to a Russian soldier in May for pre-meditated murder in the country’s first war crimes trial.

A Russian ammunition depot in the southern Kherson region had been destroyed, Ukrainian officials said on Friday.

The UK defence minister, Ben Wallace, has said Russian forces in Ukraine are in “a very difficult spot”, and that Putin’s strategy was akin to putting his forces through a meat grinder. In his opinion, he said, Russia was “certainly not able to occupy the country. They may be able to carry on killing indiscriminately and destroying as they go, but that is not a victory.”

Footage shows soldier with knife and surgical gloves mutilating prisoner as he lies down with hands bound

• Russia-Ukraine war: latest updates

Horrific video has emerged that appears to show a Russian soldier castrating a Ukrainian prisoner who other reports suggest was subsequently murdered.

The footage, reviewed by the Guardian, was originally posted on pro-Russian Telegram channels.

Ukraine says Black Sea ports ready to export grain; Kyiv calls on world leaders to condemn Russia over attack that led to death of 40 PoWs. This blog is now closed

• Ukraine seeking to get grain ships away later on Friday

On Telegram, Dmytro Zhyvytskyi, governor of Sumy in Ukraine’s north-east, has said that the night was quiet, with no air raid warnings. Maksym Kozytskyi, governor of Lviv, has said the same about his western region, posting “everything is calm”.

The same is not true for the Mykolaiv region, where in the last few minutes both the city’s mayor Oleksandr Syenkevych and regional governor Vitaliy Kim have posted to Telegram to warn that there is an air raid warning in progress.

At night, the enemy launched a rocket attack on the city of Kharkiv. An educational institution and a two-story residential building were partially destroyed, as well as nearby buildings were damaged. A fire broke out in a two-story residential building, which was promptly extinguished by rescuers.

In the Borivskyi community, rescuers put out a fire in a field with wheat on an area of 5 hectares. In addition, a man born in 1963 was injured in one of the cases of enemy hits on a residential high-rise building in the city of Chuhuiv.

Ukraine steps up campaign to retake Russian-controlled regions in south; Kyiv accuses Russia of a war crime over the deaths of more than 40 prisoners of war

• Russia-Ukraine war: see all our coverage

This live blog has now closed, you can find our latest Ukraine war coverage here

Kirill Stremousov, deputy head of the Russian-imposed military-civilian administration in the occupied Kherson region of Ukraine has posted to Telegram this morning to say that “all stories about successful ‘Ukronazi’ counter-offensives in the Kherson region are sheer lies.”

He offered no evidence to support the claim.

Educational institutions and residential buildings were damaged by rocket attacks today. Russian terrorists are cynically shelling the civilian infrastructure of Mykolaiv.

Another city school was almost completely destroyed. Part of the building collapsed there. The security guard of the institution was injured. Windows and roofs were broken in nearby private houses.

Moscow has ‘definitively’ lost initiative in battle for eastern region; Ukraine attacks key Russian held bridge in Kherson

• What we know on day 154 of the invasion

Peter Beaumont in Kyiv has filed this report on a night when it appears that Ukraine has stepped up attacks on Russian-occupied Kherson:

A key Russian held bridge into the occupied southern city of Kherson was hit with a barrage of rocket fire by Ukrainian forces who appeared to be stepping up operations to isolate the city.

Ukrainian forces strike Antonivskiy Bridge in Russian-occupied Kherson to disrupt Moscow’s supply routes

• Russia-Ukraine war: see all our coverage

This live blog is now closed, you can find our latest coverage of the Russia-Ukraine war here

The Russian state-controlled energy company Gazprom has announced a drastic cut to gas deliveries through its main pipeline to Europe from Wednesday.

The Russian gas export monopoly said it was halting the operation of one of the last two operating turbines due to the “technical condition of the engine”, cutting daily gas deliveries via the Nord Stream pipeline to 33m cubic metres a day – about 20% of the pipeline’s capacity.

Today we saw another gas threat to Europe. Even despite the concession regarding the Nord Stream turbine, Russia is not going to resume gas supplies to European countries, as it is contractually obligated to do.

All this is done by Russia deliberately to make it as difficult as possible for Europeans to prepare for winter. And this is an overt gas war that Russia is waging against a united Europe - this is exactly how it should be perceived. And they don’t care what will happen to the people, how they will suffer - from hunger due to the blocking of ports or from winter cold and poverty... Or from occupation. These are just different forms of terror.

Grain exports to begin this week despite Russian attack on Odesa 12 hours after signing agreement

Ukraine has said it hopes to start exporting grain from its ports this week, despite Russia’s attack on Odesa 12 hours after Moscow agreed to allow Kyiv safe passage for the commodity.

The first ships may move from the country’s Black Sea ports within a few days, said deputy UN spokesperson Farhan Haq. Details of the procedures will soon be published by a joint coordination centre that is liaising with the shipping industry, said Haq.