Ukrainian President Volodymyr Zelensky has demanded tougher sanctions and support fending off the Russian invasion as Kyiv was hit by air strikes as fighting closed in on the capital.

After holding talks with Boris Johnson on Friday morning, Mr Zelensky also called for allies to provide “effective counteraction” against Moscow’s advances.

Downing Street said the Prime Minister pledged further support “in the coming days” after the president updated him on the “terrible developments” in the Ukrainian capital.

Mr Johnson will use an extraordinary summit of leaders of the Nato defence alliance on Friday afternoon to press for Russia to be excluded from the Swift international payment system amid opposition to the move in the European Union.

Defence Secretary Ben Wallace said more than 450 Russian troops had been killed, as a fierce resistance meant Moscow “failed” on the main objective on the first day of fighting.

Mr Johnson and Mr Zelensky spoke after Kyiv was hit by “horrific rocket strikes” and fighting reached the outskirts of the capital overnight, before gunfire was reported in the city centre.

After the call, the president said Ukraine “needs the support of partners more than ever”.

“We demand effective counteraction to the Russian Federation. Sanctions must be further strengthened,” Mr Zelensky added.

In other developments:

– Uefa stripped St Petersburg of May’s Champions League final and handed it to Paris, while Formula One bosses cancelled the Russian Grand Prix.

– Russia retaliated to the ban on Aeroflot flights landing in the UK by banning British flights to and over Russia.

– Defence minister James Heappey told MPs the Royal Welsh battlegroup will be arriving in Estonia earlier than planned to “double up” force levels to support the Nato ally.

Mr Johnson was under growing pressure to strengthen sanctions against Russia after unveiling what he called the “largest and most severe” package of measures Russia has faced to punish Vladimir Putin, hitting further oligarchs and freezing Russian bank assets.

The Prime Minister assured Mr Zelensky during their call that “the world is united in its horror at what Putin is doing” and praised the “bravery and heroism of the Ukrainian people”, No 10 said.

“The Prime Minister committed to provide further UK support to Ukraine in the coming days as the people of Ukraine and the world continue to demonstrate that Putin cannot act with impunity,” a statement added.

A spokesman for Mr Johnson could not provide details of what support will be despatched, but said “nothing is off the table”.

Ukrainian foreign minister Dmytro Kuleba said just before 4am on Friday that “horrific rocket strikes” had hit Kyiv in an attack he compared to the city’s 1941 shelling by Nazi Germany.

Mr Zelensky said “subversive groups” were encroaching on Kyiv, as US secretary of state Antony Blinken said Kyiv “could well be under siege”.

US officials believe the action is an attempt by Russian President Mr Putin to dismantle Ukraine’s government and replace it with his own puppet regime.

The Kremlin’s long-feared assault began in the early hours of Thursday, but the British Ministry of Defence said a “fierce resistance” was holding up the Russian advance.

Mr Wallace told Sky News: “Our assessment as of this morning is that Russia has not taken any of its major objectives, in fact it is behind its hoped-for timetable.

“They’ve lost over 450 personnel. One of the significant airports they were trying to capture with their elite Spetsnaz has failed to be taken. In fact, the Ukrainians have taken it back.

“So, I think contrary to great Russian claims and indeed President Putin’s sort of vision that somehow the Ukrainians would be liberated and would be flocking to his cause – he’s got that completely wrong. The Russian army has failed to deliver on day one its main objective.”

Mr Wallace ruled out Britain helping enforce a no-fly zone over Ukraine because the RAF fighting Russian jets would trigger a “war across Europe”.

“He is trying to invade Ukraine. He won’t stop after Ukraine. He will use everything in the Baltic states. He doesn’t believe the Baltic states are really countries,” he told BBC Radio 4’s Today programme.

“And we will have to stand up to it. Now, I cannot trigger a European war and I won’t trigger a European war but what I will do is help Ukraine fight every street with every piece of equipment we can get to them, and we will support them, and that is the reality.”

Britain, the US and the EU have hit Moscow with a concerted package of economic sanctions, but are facing calls to go further to exclude Russia from Swift, a move strongly backed by Mr Johnson but facing resistance from allies including Germany and the Netherlands.

The spokesman for the Prime Minister said “we will continue to work with allies to try and cut Russia off from Swift” to deliver a “severe blow to the Russian economy” and said Mr Johnson would raise the issue at the virtual Nato summit.

Mr Wallace said Britain will “work all day” to secure Russia’s exclusion from the international payment system, telling Today: “We want it switched off. Other countries do not. We only have so many options. We are going to work all day to try and get it.”

Among the new UK sanctions introduced were measures to hit five further oligarchs, including the Russian president’s former son-in-law, and to target more than 100 businesses and individuals.

In the US, President Joe Biden was targeting Russian banks, oligarchs and high-tech sectors, while deploying more troops to Germany to bolster Nato.

Mr Zelensky said in an address early on Friday that sanctions alone were not doing enough to deter Russia.

“This morning we are defending our state alone. Like yesterday, the world’s most powerful forces are watching from afar,” he said.

“Was Russia convinced by yesterday’s sanctions? We hear in our sky and see on our earth that this was not enough.”