Western allies have sought to stage a show of unity as Russian forces close in on Kiev amid fears a European capital is about to be engulfed in a devastating conflict.

US President Joe Biden has signed a memorandum to provide up to $600m (£448m) in ‘immediate military assistance’ to Ukraine as Kyiv officials warn street fighting were underway against Russian forces in the city.

Ukraine’s president turned down a US offer to evacuate him from Kyiv hours after the UK, US and EU announced plans to impose personal sanctions on President Vladimir Putin and his minister of Foreign Affairs Sergey Lavrov in response to the Kremlin assault on Ukraine.

Mr. Biden’s subsequent memorandum directed Secretary of State Antony Blinken to provide, subject to the Foreign Assistance Act of 1961, “immediate military assistance to Ukraine” of up to $250 million (187 million) “in assistance without regard to any provision of law”. ‘to military education and training’.

It came as Kyiv authorities urged residents to seek or stay in shelters, avoid going near windows or on balconies, and take precautions not to be hit by debris or debris. balls.

As Ukrainians continued to flee across their borders, Boris Johnson said he would introduce measures “immediately”, while the White House and Brussels said they would freeze the assets of Mr Putin and his Minister for Foreign Affairs. Foreign Affairs, Mr. Lavrov.

Britain said it was also extending a ban on Aeroflot flights landing in the UK to cover Russian private jets favored by Moscow oligarchs.

At a meeting of the United Nations Security Council in New York, Russia – as expected – used its veto to block a motion calling on Moscow to cease the attack and withdraw its troops.

UK Ambassador to the UN Dame Barbara Woodward called the veto ‘absurd’ and said Russia was ‘isolated’, adding: ‘History will remember how we voted today and which countries have stood up to be counted in defense of the Charter and sovereignty. and territorial integrity of Ukraine.

Western capitals were disappointed that India and the United Arab Emirates joined China in abstaining, weakening the international spectacle of opposition to Russia’s actions.

Foreign Secretary Liz Truss also noted Russia’s isolation and called Moscow a “global pariah”.

“Putin’s invasion of Ukraine and violation of the UN Charter will have serious consequences,” Ms. Truss added.

Despite the escalation of economic measures, there is no indication that they are having an impact on Mr Putin’s determination to continue his military offensive against his neighbor which began on Thursday.

Western officials have expressed concern that Russia could deploy devastating thermobaric weapons, amid signs that its advance has been slower than expected in the face of strong Ukrainian resistance.

So-called “vacuum bombs” suck in oxygen to create powerful, high-temperature explosions that can damage internal organs.

“My fear would be that if they don’t stick to their schedule and goals, they would use violence indiscriminately,” an official said.

The latest intelligence update from the Ministry of Defense in London said Russian forces had made progress through Friday – with a likely amphibious landing in southern Ukraine around Mariupol.

However, the main target remains Kiev, with Russian forces advancing on “several axes” in an attempt to encircle the city.

With reports of sporadic fighting in the suburbs, heavy civilian casualties are feared as the bulk of Russian troops reach the capital.

Britain’s head of defense intelligence, Lieutenant-General Sir Jim Hockenhull, said their aim was “to secure control of the population and change the regime”.

After President Putin called on Ukrainian troops to rise up against their leaders and stop fighting, Mr Johnson issued his own appeal to the Russian people.

In a video posted to social media, he warned that their country was facing “complete isolation” following their leader’s “useless and bloody war” which would mean many Russian soldiers “will not see again never their family”.

Speaking briefly in Russian, he said, “I don’t believe this war is in your name.”

At a virtual summit of NATO leaders on Friday, they agreed to send elements of the 40,000-strong alliance response force to protect eastern member states, fearing they could be the next target of Russian aggression.

NATO Secretary General Jens Stoltenberg said it was clear the Kremlin’s goals “are not limited to Ukraine” and that they “would do what it takes to protect and defend every ally and every square centimeter of NATO territory”.

“We are facing a new normal in European security where Russia openly challenges the European security order and uses force to pursue its goals,” he said.

Meanwhile, Facebook said it “prohibits Russian state media from running ads or monetizing on our platform anywhere in the world.”

What we know so far:

• Putin mocks Macron’s calls for peace.
• Russian troops are in the northern districts of Kiev.
• The Ukrainian government calls on citizens to make Molotov cocktails and defend the city.
• 450 Russian soldiers killed in the fighting.
• At least 25 civilians killed and 102 injured in airstrikes.
• The United Kingdom has been asked to help stop Russia’s assault.