The Ukrainian navy claims it has struck a Russian boat carrying air defence systems to a strategic island in the Black Sea.

The navy said the Vasily Bekh was used to transport ammunition, weapons and personnel to Snake Island, which is vital for protecting sea lanes out of the key port of Odesa.

It did not say how much damage it inflicted with the strike.

Snake Island, 20 miles off the coast, figured memorably early in the war when Ukrainian border guards stationed there defied Russian orders to surrender, using colourful language that later became a rallying cry.

The flagship of Russia’s Black Sea fleet, used in the seizure of Snake Island, was sunk in April by Ukraine — a major coup for the outmanned and outgunned Ukrainian forces, which used technology and intelligence from the US to target the ship.

The Ukrainian navy said on Friday that after the sinking of the flagship Moskva, the Russians began to install an anti-aircraft missile system called TOR on the decks of their ships.

It said that was not enough to prevent Ukraine’s naval forces from “demilitarising the Russian occupiers”.

There was no immediate reaction from Russian authorities about the Ukrainian claim.

At Russia’s showpiece economic forum in St Petersburg on Friday, President Vladimir Putin reprised his usual defence of the Kremlin’s war in Ukraine, falsely claiming that it was an act of self-defence.

He has insisted before that his invasion was necessary to protect people in parts of eastern Ukraine controlled by Moscow-backed rebels and to ensure Russia’s own security.

A group of volunteers called the IT Army of Ukraine took credit for a cyberattack that delayed Mr Putin’s speech.

The group, convened by Ukraine after the invasion to launch cyberattacks against Russian targets, said it carried out a distributed denial-of-service attack, which leverages networks of zombie computers to flood websites with junk traffic, rendering them unreachable.

Despite the apparent success, Ukraine has urged its allies to rush more and better weapons to the country, saying it cannot hold off Russia’s more powerful forces without more support.

Western weapons have been critical to the embattled nation’s surprising success so far.

Russia pressed its offensive in the country’s eastern Donbas region on Friday, leaving desperate residents struggling to make sense of what the future holds for them.

“We are old people, we do not have a place to go. Where will I go?” asked Vira Miedientseva, one of the elderly residents grappling with the aftermath of an attack on Thursday in Lysychansk, which lies just across the river from Sievierodonetsk, a key focus of battles in recent weeks that Russians have nearly captured.

After a series of setbacks early in the war, including the failure to seize Ukraine’s capital, Russian forces have switched their focus to the Donbas, pressing a grinding offensive.

In recent weeks, they have moved in on Sievierodonetsk and surrounding villages — the last pocket of the Luhansk region not yet claimed by Russia or its allies.

“The Russians are pouring fire on the city,” said Luhansk governor Serhiy Haidai. “It’s getting harder and harder for us to fight in Sievierodonetsk, because the Russians outnumber us in artillery and manpower, and it’s very difficult for us to resist this barrage of fire.”

The constant shelling made it impossible for 568 people, including 38 children, sheltering in the Azot chemical plant in the city to escape, he said.

Russian forces have destroyed all three bridges leading out of the city, but Mr Haidai said it had still not been fully blocked off.

The Moscow envoy for Russia-backed separatists who control much of the territory around Sievierodonetsk said an evacuation from the Azot plant could take place, under certain conditions.

Writing on social media on Friday, Rodion Miroshnik of the self-proclaimed Luhansk’s People’s Republic, said Russian troops and separatists are “ready to consider options for opening a humanitarian corridor for the exit of civilians, but subject to strict adherence to the ceasefire”.

Earlier this week, Mr Miroshnik accused Kyiv’s troops of trying to disrupt the evacuation of civilians from Azot, a claim denied by Ukrainian officials.

Kyiv has also pushed for increased political support, including a fast track to membership in the European Union.

On a visit to Ukraine on Thursday, four European Union leaders vowed to back Kyiv’s candidacy to eventually join the bloc. The European Commission is set to meet on Friday to make its official recommendation.

The war has increased pressure on EU governments to move more quickly on Ukraine’s candidate status, and Thursday’s pledge to support candidacy status for Ukraine and neighbouring Moldova pushes the 27-nation union closer to doing so.

But the process is expected to take years, and EU members remain divided over how quickly and fully to open their arms to new members.