Ukraine military chiefs say Russia is continuing its 'full-scale armed aggression': Putin's forces 'encircle' Ukrainian soldiers in east and missiles hit food and fuel depots - as Moscow orders more troops to border amid fears of further advances

 Russian troops are trying to encircle Ukrainian forces fighting in the separatist regions in the eastern part of the country, British intelligence chiefs said, as Russia continues its attacks on Ukraine.  

Vladimir Putin's forces are advancing southward from the area around the city of Kharkiv and north from the port city of Mariupol to the Donbas region in an attempt to surround Ukrainian troops, the Ministry of Defence said in an intelligence briefing today.

But in a further blow to Putin's barbaric invasion, Ukrainian forces repulsed seven attacks in the eastern regions of Donetsk and Luhansk and destroyed several tanks and armoured vehicles, the General Staff of Ukraine's Armed Forces said on Sunday. 

Ukraine's military chiefs said on Sunday that Russia is continuing with its 'full-scale armed aggression', with rocket attacks being launched on Ukrainian cities overnight. 

Russian missiles struck Ukrainian fuel and food storage depots in the city of Lviv, sparking huge fires and wounding at least five people. 

A security guard at the site, Yaroslav Prokopiv, said he saw three rockets strike and destroy two oil tanks. 'The third strike threw me to the ground,' he said.

The attack on the facilities means the government will have to disperse the stocks of both in the near future, Ukrainian Interior Ministry adviser Vadym Denysenko said today.   

Denysenko also said Russia was bringing forces to the Ukrainian border on rotation, and could make new attempts to advance in its invasion of Ukraine.

Western intelligence officials say Russian forces now rely on indiscriminate bombardments rather than risking large-scale ground operations, a tactic that could limit Russian military casualties but would harm more civilians.

Whilst Russian troops appear to be advancing on the Donbas region in eastern Ukraine, battlefields in northern Ukraine remain 'largely static,' with Ukrainian counterattacks hampering Russian efforts to reorganise their forces, the UK's MoD said.

It comes as President Joe Biden last night called for Putin to be removed from power, setting off alarm bells among US foreign policy experts, who fear that it could escalate tensions.  

'For God's sake this man cannot remain in power,' Biden said in a shocking apparent call for regime change in Moscow at the end of a impassioned speech from Poland on Saturday.  

Ukrainian firefighters try to contain a major fire after Russian missiles struck a fuel storage facility in the western Ukrainian city of Lviv on March 26

Dark smoke and flames rise from a fire following an air strike in the western Ukrainian city of Lviv on Saturday

Russian servicemen drive on the infantry armoured vehicles in downtown Volnovakha, near Donetsk, Ukraine, on Saturday

Vladimir Putin's forces are advancing southward from the area around the city of Kharkiv and north from the port city of Mariupol to the Donbas region in an attempt to surround Ukrainian troops, the MoD said in an intelligence briefing today

Russian missiles struck Ukrainian fuel and food storage depots in the city of Lviv, sparking huge fires and wounding at least five people

Firefighters try to extinguish the fire as the flames and smoke rise after Russian guided missiles hit fuel tanks attacks in Lviv

A satellite image made available by Maxar Technologies shows damage to Ukrainian fuel storage depot at Kalynivka, Ukraine

President Joe Biden's call for Vladimir Putin to be removed from power in Russia is setting off alarm bells among foreign policy experts. who fear that it could escalate tensions

'For god's sake this man cannot remain in power,' he said of Putin, describing the Russian president as having a 'craving for absolute power and control.'

A wrecked tank is seen near a damaged building in Mariupol on Saturday as civilians are being evacuated along humanitarian corridors from the Ukrainian city under the control of Russian military and pro-Russian separatists

The unscripted remark, which the White House scrambled to walk back as the Kremlin expressed fury, came at the end of an otherwise resolute and fiery speech in Poland rallying the free world to unite in opposition to autocracy and support of Ukraine.  

Meanwhile, in the encircled southern port of Mariupol, Mayor Vadym Boichenko said the situation remained critical, with street fighting in the centre. 

Russia said last week it had evacuated several hundred thousand people from the war zone, but Ukraine says thousands of its residents, including from Mariupol, have been illegally deported.

Ukraine and Russia have since agreed on two 'humanitarian corridors' to evacuate civilians from frontline areas on Sunday, including allowing people to leave by private car from the southern city of Mariupol, Deputy Prime Minister Iryna Vereshchuk said.

But there are fears over whether Russia will adhere to allowing Ukrainian citizens to leave via the humanitarian corridors, after previous Russian attacks have killed civilians fleeing via those routes.      

Meanwhile Russian forces on Saturday seized Slavutych, a town where workers at the defunct Chernobyl nuclear plant live, and the mayor said three people were killed, Interfax Ukraine news agency reported.

Ukrainian staff have continued to work at Chernobyl after the site of the world's worst nuclear accident was seized by Russian forces. 

Ukraine's nuclear watchdog said that a nuclear research facility in Kharkiv again has come under shelling by Russia and the fighting makes it impossible to assess the damage.

The State Nuclear Regulatory Inspectorate said that the neutron source experimental facility in the Kharkiv Institute of Physics and Technology came under fire Saturday.

Ukrainian authorities have previously reported that Russian shelling damaged buildings at the Kharkiv facility, but there has been no release of radiation. The newly built neutron source facility is intended for the research and production of radioisotopes for medical and industrial needs. 

The International Atomic Energy Agency has said that the nuclear material in the facility is always subcritical and the inventory of radioactive material is very low, reducing the risks of radiation release.

Kharkiv has been besieged by Russian forces since the start of the invasion and has come under repeated shelling of its residential buildings and critical infrastructure. 

Firefighters operate at a damaged oil depot following a Russian missile attack in the city of Lviv, as Russia's attack on Ukraine continues, on Sunday

Ukrainian soldier standing before a Russian self-propelled artillery gun destroyed following a battle in the town of Trostyanets, Sumy region, on Sunday

A Russian tank destroyed following a battle in the town of Trostyanets, Sumy region, in Ukraine, on Sunday

Meanwhile, Biden was criticised for calling for Putin to be removed from power. Richard Haass, the Council on Foreign Relations president, tweeted his concerns that Biden had 'just expanded US war aims, calling for regime change.' 

'However desirable it may be, it is not within our power to accomplish-plus runs risk it will increase Putin's inclination to see this as a fight to the finish, raising odds he will reject compromise, escalate, or both,' wrote Haass.

'Our interests are to end the war on terms Ukraine can accept & to discourage Russian escalation. Today's call for regime change is inconsistent with these ends,' he added. 

Haass went on to tell Politico that a senior Biden official, possibly even Secretary of State Antony Blinken, needs to reach out to their Russian counterpart immediately and explain that Biden's comment doesn't reflect US policy.

'The fact that it was so off-script in some ways makes it worse,' because it could be read as Biden's genuine belief as opposed to his scripted words, Haas said.

Biden's remark could also diminish Putin's interest in compromise and increase his temptation to escalate in Ukraine, 'because if he believes he has everything to lose then he'll believe he has nothing to lose,' Haass said. 

Before Biden could even board Air Force One to begin the flight back to Washington, his aides were rushing to claim that he hadn't been calling for an immediate change in government in Moscow.

'The President's point was that Putin cannot be allowed to exercise power over his neighbors or the region. He was not discussing Putin's power in Russia, or regime change,' a White House official said. 

Kremlin spokesman Dmitry Peskov quickly denounced Biden, saying 'it´s not up to the president of the U.S. and not up to the Americans to decide who will remain in power in Russia.' 

Biden's alarming off-the-cuff remark comes just 24 hours after the White House rushed to clarify other awkward remarks from the president suggesting that US troops would deploy, and had already deployed, to Ukraine.

In a speech to US paratroopers in Poland on Friday, Biden said: 'You're going to see when you're there – some of you have been there – you're going to see women, young people, standing in the middle, in front of a damn tank, saying, 'I'm not leaving'.'

Biden's mention of 'when you're there' seem to suggest that the troops would be deployed across the border to Ukraine, but the administration insisted there has been no change in his stance that the US will not enter the conflict. 

The White House was forced to clarify on Friday that American troops would not be going into Ukraine after President Biden appeared to make a slip in his speech to paratroopers in Poland

'The president has been clear we are not sending U.S. troops to Ukraine and there is no change in that position,' a White House spokesperson clarified to Fox News on Friday.

Biden has persistently said that troops would not be sent into Ukraine under any circumstances during Putin's invasion, fearing it would turn into World War Three and end up becoming a lengthy combat mission like in Afghanistan. 

In his fiery speech on Saturday, Biden drew a stark line between democracy and oppression, repeatedly going after Putin and accusing the Russian president of dishonesty.

Speaking outdoors in the cobbled courtyard of the Royal Castle in Warsaw, which was lit with the colors of Poland and Ukraine, Biden accused Putin of 'using brute force and disinformation' to rule.

'It's nothing less than a direct challenges to the rules-based system of international order,' Biden said.

President Joe Biden accused Vladimir Putin of duplicity in the run up to Russia's invasion of Ukraine

Biden also took a cue from Arnold Schwarzenegger - who released a video message to Russians that went viral - and spoke directly to the Russian people.

'I'm telling you the truth. This war is not worthy of you the Russian people,' he said. 'Putin can and must end this war. The American people will stand with you and the brave citizens of Ukraine that want peace.'

And he warned Putin's aggression could bring 'decades of war' to Europe.

'It's nothing less than a direct challenge for the order established since the World War II and it threatens to return to decades of war that ravage Europe before the international rule-based order was put in place. We cannot go back to that,' Biden said.

Biden also moved to calm worried Eastern European nations. He made it clear the NATO alliance would hold together and he warned Russia not to think about expanding his invasion outside of Ukraine.

Poland and the old Eastern bloc nations - like Lativa and Estonia - are worried Putin's ambitions might lead to their borders. But Biden made it clear NATO would protect its member nations and honor Article Five, which states if one is striked, all respond. 

'Don't even think about moving on one single inch of NATO territory. We have sacred obligations,' Biden said.

Biden mentioned his own conversations with Putin before Russia's invasion late last month.

He said Putin 'repeatedly he asserted he had no interest in war - guaranteed he would not move.'

'There is simply no justification or provocation for Russia's choice of war.

President Biden walks out on stage to give his remarks at the Royal Castle in Warsaw

President Joe Biden boards Air Force One, heading back to Washington D.C. 

Polish President Andrzej Duda listens as President Joe Biden delivers a speech about the Russian invasion of Ukraine, at the Royal Castle

But Putin and Russia met each of the proposals with disinterest. 'Russia was bent on violence from the start,' he said.

After days of diplomacy and quiet meetings with powerbrokers in Warsaw and Brussels, the White House lined up a speech where Biden could speak in broad strokes about what was at stake, as the U.S. and allies rush to arm Ukraine.

Biden said the war has been 'a strategic failure for Russia already' – alluding to its battlefield losses.

'He, Putin thought Ukrainians would roll over and not fight. Not much of a student of history. Instead, Russian forces have met their match,' he said, in a speech with references to Pope John Paul II, the siege of Stalingrad, and Lech Walesa.

Despite Putin's aims, 'The west is not stronger and more united than it has ever been,' Biden said, pointing to the international response,' Biden said.

'The democracies of the world are revitalized,' said Biden. 

People listen as President Joe Biden delivers a speech about the Russian invasion of Ukraine

In contrast, he said Russia was suffering a 'remarkable brain drain,' with more than 200,000 leaving the country in a month.

'We must commit now to be in this fight for the long haul,' he said, speaking in a country that has been pushing to arm Ukraine while housing more than 2 million refugees.

Punctuating his words, he told a cheering crowd never to be discouraged. 'Be not afraid,' he said.

Ukraine will never be a victory for Russia,' he vowed. 'For God's sake, this man cannot remain in power,' he said, on a day when Russia lobbed new missiles at Lviv in western Ukraine.

Biden began and ended his remarks with a quote from the first Polish pope, Pope John Paul II, telling people: 'Be not afraid.'

Biden has personally attacked Putin before, calling him a war criminal and said he doesn't have a soul.

Earlier Saturday, he called Putin a 'butcher' after holding emotional conversations with Ukrainian refugees – including a pair who fled the horror of the siege at Mariupol.

'He's a butcher,' Biden said when asked what he thought of Putin after what he has done to the people he was meeting.