Russia's defence ministry has said the last group of Ukrainian forces holed up in Mariupol's destroyed Azovstal steel works had surrendered, marking an end to a weeks-long siege.

"The territory of the Azovstal metallurgical plant ... has been completely liberated," the ministry said in a statement. It said the group that had given up comprised 531 people.

The full abandonment of the bunkers and tunnels of the bombed-out plant means an end to most destructive siege of a war that began when Russia invaded Ukraine nearly three months ago.

Ukraine ordered the garrison to stand down on Monday. Hours before the Russian announcement, President Volodymyr Zelensky said the defenders had been told by Ukraine's military that they could get out and save their lives and would most likely all leave in the coming days.

Earlier today, Russian troops bombarded a riverside city in what appeared to herald a major assault to seize the last remaining Ukrainian-held territory in a province it claims on behalf of separatists.

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Ukrainian officials said Russian forces had launched massive artillery bombardment against Sievierodonetsk, one of the last Ukrainian-held bastions in Luhansk, one of two southeastern provinces Moscow and its proxies proclaim as independent states.

The city, and its twin Lyshchansk on the opposite bank of the Siverskiy Donets river, form the eastern part of a Ukrainian-held pocket that Russia has been trying to overrun since mid-April after failing to capture the capital Kyiv.

Ukraine's general staff said Moscow had launched an offensive on Sievierodonetsk but had taken losses and was forced to retreat, part of what it described as major Russian offensive operations along a stretch of the frontline.

Despite losing ground elsewhere in recent weeks, Russian forces have advanced on the Luhansk front, in what some military analysts view as a major push to achieve scaled-down war aims of capturing all territory claimed by pro-Russian rebels.

"The Russian army has started very intensive destruction of the town of Sievierodonetsk, the intensity of shelling doubled, they are shelling residential quarters, destroying house by house," Luhansk governor Serhiy Gaidai said via his Telegram channel.

"We do not know how many people died, because it is simply impossible to go through and look at every apartment," he said.

In Moscow, Russian Defence Minister Sergei Shoigu said the "liberation of the Luhansk People's Republic" would be completed soon.

Conditions in the Donbas 'hell' - Zelensky

In an overnight address, Ukrainian President Volodymyr Zelensky described the conditions in the Donbas, which includes Luhansk and neighbouring Donetsk province, as "hell" and said the region had been "completely destroyed" by Russia's invasion.

Capturing Luhansk and Donetsk would allow Moscow to claim victory after it announced last month that this was now its objective. It achieved a major step towards that goal this week, when Ukraine ordered its garrison in the main Donbas port, Mariupol, to stand down after a near three-month siege.

Russia's Shoigu said around 2,000 Ukrainian fighters had surrendered in the past four days.

Kyiv has not confirmed how many fighters have surrendered, but Britain gave the first official Western confirmation that a large force had indeed laid down arms, saying around 1,700 had surrendered. An unknown number of others were still believed to be inside, it said.

In a video, the commander of the Azov Batalion, a Ukrainian unit that had defended the plant, confirmed the order to stop fighting was being carried out, and said all civilians and wounded fighters were now out.

Denys Prokopenko, the commander, gave no further details of the fate of other fighters, but said a process was under way to remove the dead from the warren of underground tunnels and bunkers.

"I hope that in the near future, relatives and Ukraine will be able to bury their soldiers with honour," Prokopenko said.

The Red Cross says it has registered hundreds of prisoners of war who surrendered at the plant, but has given no firm numbers or further details.

Kyiv says it wants to arrange a prisoner swap for Azovstal defenders it describes as national heroes. Moscow says they will be treated humanely, but Russian politicians have been quoted as saying some must be tried for crimes or even executed.

A Russian soldier seen in an armoured vehicle on a roadside in the Kherson region

The past week has seen Sweden and Finland apply to join NATO, the biggest shakeup in European security for decades, although Turkey has so far said it will block the move, accusing the Nordic countries of harbouring Kurdish militants.

After weeks of threatening to retaliate, Putin appears to have climbed down, saying this week that NATO membership for Finland and Sweden did not represent a threat as such, unless the alliance sends new weapons or troops. Nevertheless, Defence Minister Shoigu said on Friday Moscow planned to beef up its forces nearby in response to what he called new threats.

Russian forces in Ukraine have been driven in recent weeks out of the area around Ukraine's second largest city Kharkiv, their fastest retreat since being forced out of the north and the area around Kyiv at the end of March.

But they still control a large swathe of the south and east, and the end of fighting in Mariupol means that territory is now largely unbroken. Still, military analysts say Russia has been using up its offensive firepower and may be running out of time to achieve its aim of capturing the entire Donbas.

Russian servicemen on a roadside in the Kherson region yesterday

In a sign of Russia's aim to boost its war effort, the parliament in Moscow said it would consider a bill to allow Russians over 40 and foreigners over 30 to sign up for the military.

Putin has stopped short of declaring his "special military operation" to be a war, which would make it easier to mobilise reservists and conscripts.

Ceann Comhairle meets Zelensky in Kyiv

Meanwhile, Mr Zelensky today met with an Irish delegation in Kyiv, which included Ceann Comhairle Seán Ó Fearghail and Cathaoirleach of the Seanad Mark Daly.

Mr Zelensky said the visit was a signal of Ireland's support of Ukraine.

"It is very important for us that Europe remains united, because in this unity, there is also the strength of our state, as we demonstrated when our people united against the Russian aggression," he said.

"Similarly, unity from the European side is also important, important not only in supporting Ukraine, but also in taking steps against Russia, mainly with the sanctions."

In a video shared on Twitter by the Ukrainian Embassy in Ireland, Mr Ó Fearghail praised Mr Zelensky for "the determination you are showing to the world".

"Let us be advocates for your great country," he added.

Mr Ó Fearghail and Mr Daly also met with Ukrainian Prime Minister Denys Shmyhal. On social media, Mr Shmyhal said they discussed the global food crisis, demining of territory and Ukraine's recovery plan.

Western support

Western powers, who have strongly condemned Russia's actions and sought to isolate Moscow with an array of sanctions, were stepping up their support for Ukraine.

The Group of Seven rich nations yesterday agreed to provide Ukraine with $18.4 billion to make up for lost revenues as the war wrecks its economy.

The US Senate approved nearly $40 billion in new aid for Ukraine, by far the largest US aid package to date.

The White House is also working to put advanced anti-ship missiles in the hands of Ukrainian fighters to help defeat Russia's naval blockade, which has largely stopped Ukraine's exports of food.

US President Joe Biden has cast the Ukraine war as part of a great US-led struggle of democracy against authoritarianism.

President of Finland Sauli Niinistö (L) Joe Biden and
Prime Minister of Sweden Magdalena Andersson (R) at the White House in Washington DC

Mr Biden offered "full, total, complete backing" to Finland and Sweden in their bid to join the NATO military alliance, when he gave their leaders a red-carpet welcome at the White House yesterday.

'We're not idiots'

But all 30 existing NATO members need to agree on any new entrants and Turkey has condemned the historically non-aligned Nordic neighbours' alleged toleration of Kurdish militants.

Russian Defence Minister Sergei Shoigu said the Kremlin would respond to any NATO expansion by creating more military bases in western Russia.

As well as redrawing the security map of Europe, the conflict has sent shockwaves through the global economy, especially in energy and food markets.

Russia and Ukraine produce 30% of the world's wheat supply and the war has sent food prices surging. Russia is also a major exporter of fertiliser.

United Nations Secretary-General Antonio Guterres warned the war could trigger years of "famine" in poorer parts of the world.

Washington urged Russia to allow exports of Ukrainian grain held up at Black Sea ports.

But former Russian president Dmitry Medvedev blamed the West.

"On the one hand, insane sanctions are being imposed against us. On the other hand, they are demanding food supplies," he said. "Things don't work like that. We're not idiots."

The war has caused global prices for grains, cooking oils, fuel and fertiliser to soar.

The EU said it is looking into ways of using the frozen assets of Russian oligarchs to fund the reconstruction of Ukraine, while the United States has not ruled out possibly placing sanctions on countries that purchase Russian oil.

Elsewhere, Russian supply of natural gas to Finland will be cut tomorrow morning, Finnish state-owned energy company Gasum said, after the Nordic country refused to pay supplier Gazprom in rubles.