All vulnerable civilians have been evacuated from the Azovstal steelworks holdout in Mariupol, Ukraine said Saturday, presaging a showdown between Kyiv's last remaining soldiers there and the besieging Russian forces ahead of celebrations marking the Soviet World War II victory.

The steel mill, the final pocket of Ukrainian resistance in the devastated port city, has taken on a symbolic value in the war. Kyiv fears a renewed intensity to Moscow's offensive.

"All women, children and the elderly have been evacuated from Azovstal," Deputy Prime Minister Iryna Vereshchuk said.

During a speech, Ukrainian President Volodymyr Zelensky said that hundreds of people had been removed from the plant and that preparations for a second stage of evacuation comprising the wounded and medics were under way.

Fighting continues on many fronts, and Ukraine's defence ministry said it had destroyed another Russian vessel -- a Serna-class landing craft -- in the Black Sea.

"The traditional parade of the Russian Black Sea fleet on May 9 this year will be held near Snake Island -- at the bottom of the sea," the ministry added. Russia did not immediately confirm the incident.

Earlier, Ukraine's defence ministry said Russian forces had resumed their assault on the Azovstal site, despite talk of a truce to allow trapped civilians to flee.

- Putin may be 'doubling down' -

On Monday, President Vladimir Putin will celebrate the World War II Soviet victory over Nazi Germany with a traditional Victory Day parade.

According to Russia's defence ministry, 77 aircraft will conduct a fly-past, including the rarely seen Il-80 Doomsday plane that can withstand a nuclear attack.

Despite apocalyptic nuclear threats carried by Russian state media, the CIA said Saturday it saw no indication Moscow was preparing to use tactical atomic weapons in the Ukraine conflict.

"We don't see, as an intelligence community, practical evidence at this point of Russian planning for the deployment or even potential use of tactical nuclear weapons," CIA director Bill Burns said at a conference.

Burns also warned that Putin believed he could not afford defeat in Ukraine and that he might be "doubling down" on the offensive.

Eight Mig-29 fighter jets will fly over Moscow's Red Square during Monday's festivities, forming the letter "Z" -- the mark of Russia's military assault in Ukraine. 

The Russian campaign has run into tough resistance -- and galvanised Kyiv's western allies to comprehensively sanction the Russian economy and Putin's inner circle.

But with Victory Day approaching, Ukrainian officials fear more intense missile and artillery bombardments and renewed assaults, as Moscow scrambles for symbolic wins.

- 'Massive bombardments' -

The Ukrainian rescue service said a missile had hit a technical college in Kostiantynivka, in the eastern region of Donetsk, killing at least two people. 

Donetsk regional governor Pavlo Kyrylenko reported "massive bombardments" along the frontline.

Four civilians had been killed in Donetsk, two in Bakhmut and two in Kostiantynivka, with another nine people wounded, he added.

Ukrainian forces, meanwhile, have launched a counter-offensive.

According to the defence ministry, Russian troops were forced to demolish three road bridges near Tsyrkuny and Ruski Tyshky outside Kharkiv, to slow the Ukrainian advance.

Zelensky said Saturday that a Russian missile has struck a museum in the Kharkiv region, announcing that the "Russian army destroyed or damaged nearly 200 cultural heritage sites already."

British intelligence said Ukrainian forces equipped with high-end weaponry by western allies have been able to destroy at least one of Russia's most advanced tanks, the T-90M.

"The conflict in Ukraine is taking a heavy toll on some of Russia's most capable units and most advanced capabilities," UK Defence Intelligence said.

"It will take considerable time and expense for Russia to reconstitute its armed forces following this conflict," it said, adding that sanctions on advanced components would make it harder for Russia to re-arm.

- Western aid -

G7 leaders, including US President Joe Biden, and Ukraine's Zelensky will on Sunday discuss Western support for Kyiv in videoconference, after Biden on Friday announced a $150-million package of military aid.

Biden's wife, First lady Jill Biden, was in Romania Saturday meeting Ukrainian refugees. 

After listening to mothers and children recount how they fled Russia's invasion of their country, she told them: "We stand with you, I hope you know that."

Ambassadors from EU member states meet in Brussels Sunday to discuss their sixth round of economic sanctions against Moscow, which this time should include a phased ban on imports of Russian oil.

- Russia to remain 'forever' -

The last Ukrainian soldiers in the devastated Black Sea port of Mariupol are believed to be holed up in the tunnels and bunkers beneath Azovstal.

Ukraine's Azov battalion, leading the defence at steelworks, said one Ukrainian fighter had been killed and six wounded when Russian forces opened fire during an earlier attempt to evacuate people by car.

Taking full control of Mariupol would allow Moscow to create a land bridge between the Crimea peninsula, which it annexed in 2014, and separatist regions run by Russian puppets in the east.

In Lugansk, Ukrainian officials said Friday that Russian forces had almost encircled Severodonetsk -- the easternmost city still held by Kyiv -- and were trying to storm it.

Kherson in the south remains the only significant city Russia has managed to capture since the war began.

A senior official from the Russian parliament, Andrey Turchak, said during a visit to the city on Friday that Russia would remain in southern Ukraine "forever".

Latest developments

Here are the latest developments in the war in Ukraine:

- Last civilians rescued from Azovstal -

Deputy Prime Minister Iryna Vereshchuk says "all women, children and the elderly" have been evacuated from the besieged Azovstal steel plant in the destroyed port city of Mariupol. 

Kyiv urges aid agency Doctors Without Borders (MSF) to evacuate its soldiers from the steel plant, adding those wounded are "dying because of gangrene and sepsis" without medicine.

- Victory Day rehearsal -

Russia holds its final rehearsal for an annual parade marking the Soviet victory in World War II, where its military might will be showcased amid Moscow's ongoing campaign in Ukraine.

President Vladimir Putin is expected to deliver a speech during the parade, which some Western officials believe could be a declaration of all-out war on Ukraine, speculation the Kremlin has dismissed as "nonsense". 

- Ukraine says sinks Russian landing craft -

Ukraine's defence ministry says it has destroyed a Russian landing craft near the Black Sea's Snake Island, posting overhead footage on social media of what appears to be an explosion over a light craft. Russia has not yet confirmed the strike.

Snake Island became a symbol of Ukrainian resistance after its soldiers colourfully rebuffed a demand by the Russian warship Moskva to surrender.

- 'Staggering' Russian violations -

The Council of Europe's human rights commissioner, Dunja Mijatovic, calls Russian violations of human rights in Ukraine "staggering" after a four-day visit to the country. 

The visit to areas outside Kyiv illustrated "mounting evidence of widespread arbitrary killings, torture, and enforced disappearances," the council says in a statement.

- Italy impounds Putin-linked yacht -

Italy has impounded a $700 million, 140-metre mega yacht as speculation swirls it could belong to Putin.

An Italian investigation has helped establish "significant economic and business links" between the official owner of "Scheherazade", and "eminent people in the Russian government", as well as Russians on the West's sanctions list, the economy ministry says.

- Eastern city surrounded -  

Russian forces have almost encircled Severodonetsk, the easternmost city still held by Ukraine where about 15,000 people remain, a local official says.

- Jill Biden visits refugees -

US First Lady Jill Biden visits refugees from Ukraine in Romania, where women and children tell her their stories.

"We stand with you, I hope you know that," she tells them during a visit to a school in Bucharest, where she is accompanied by her Romanian counterpart Carmen Iohannis.

- New US weapons -

US President Joe Biden announces a new $150 million weapons package to Ukraine, including artillery munitions and radar, while urging Congress to pass a $33 billion aid package including $20 billion in military aid.

The new batch brings the total value of US weaponry sent by the Biden administration to Ukraine to $3.8 billion since Russia invaded on February 24, says Secretary of State Antony Blinken.