She said the UK is discussing the prospect with its allies, given Vladimir Putin has been "clear about his ambitions to create a greater Russia".

In an interview with the Telegraph, Ms Truss said the aim was to ensure Ukraine is "permanently able to defend itself", and this also applies to other "vulnerable states" such as Moldova, which is not a NATO member.

"I would want to see Moldova equipped to NATO standard," she said. "This is a discussion we're having with our allies."

Asked if this is because Russia poses a security threat to Moldova, she replied: "Absolutely. I mean, Putin has been clear about his ambitions to create a greater Russia.

"And just because his attempts to take Kyiv weren't successful doesn't mean he's abandoned those ambitions."

Russia claims to have taken control of the Ukrainian port city of Mariupol, with Moscow facing calls to be held financially responsible for "crimes it has committed" in Ukraine.

President Volodymyr Zelenskyy called on allies to sign a multi-lateral agreement to push for it to happen - as "evil must be answered".

In his nightly address, he said it was an important step not only "in the context of this war", but also "in the context of any other aggressive actions, whether by Russia or any other potential aggressor.

"Evil must be answered and know that it will be punished," he added.

Other key developments:
• Russia is thought to be experiencing a shortage of drones for reconnaissance strikes on jets and artillery, the UK's Ministry of Defence says
• Britain's Royal Family are reportedly providing accommodation to Ukrainian families forced to flee their homeland
• Three people were reportedly killed after Russian forces fired at a school in the eastern Ukrainian city of Severodonetsk
• A semi-naked protester painted in the colours of the Ukrainian flag was removed from the Cannes Film Festival red carpet
• Chess grandmaster Garry Kasparov and former oil tycoon Mikhail Khodorkovsky have been added to Russia's list of individuals acting as "foreign agents", the Kremlin said
• Wimbledon has been stripped of its ranking points by world tennis authorities after it banned players from Russia and Belarus from competing at the tournament this year

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Russian 'liberation'

On Friday, convoys of buses carrying Ukrainian fighters left the Azovstal steel plant, as Russia claimed to have taken full control of Mariupol.

Russian defence minister Sergei Shoigu reported to President Putin the "complete liberation" of the Azovstal steel plant in Mariupol - the last stronghold of Ukrainian resistance - and the city as a whole, spokesman Igor Konashenkov said.

There was no immediate confirmation from Ukraine.

Read more: The site where 'hundreds' of Russians were killed after botched attempt to cross river

Mr Konashenkov said a total of 2,439 Ukrainian fighters who had been holed up at the steelworks had surrendered since Monday, including more than 500 on Friday.

As they surrendered, the troops were taken prisoner by the Russians, and at least some were taken to a former penal colony. Others were said to have been taken to hospital where Moscow said they had been treated.