Photograph: Serhii Nuzhnenko/AP© Provided by The Guardian Photograph: Serhii Nuzhnenko/APAs US president Joe Biden warned Vladimir Putin that he would “pay a price” for his aggression, the Russia leader’s forces have shown no sign of stopping an assault that has included strikes on the capital Kyiv and rocket attacks in the second city of Kharkiv, resulting in the deaths of dozens of people.In a ringing attack on Putin in his State of the Union address on Tuesday night, Biden told the massed members of US Congress in Washington that the invasion of Ukraine had left Russia “weaker, and the rest of the world stronger.”

“Throughout our history we’ve learned this lesson – when dictators do not pay a price for their aggression, they cause more chaos. They keep moving. And, the costs and threats to America and the world keep rising.

“Putin has unleashed violence and chaos. But while he may make gains on the battlefield – he will pay a continuing high price over the long run.”

Biden announced he was banning Russian flights from US airspace from Wednesday. Ukraine’s ambassador to the US got a standing ovation at the start of the address, as Biden called on the House to show the world that the United States of America stands with Ukraine.

Facing emboldened Ukrainian troops bolstered by citizen soldiers, Russia has failed to capture a single city since its full-scale invasion began nearly a week ago. Western analysts say Russia has resorted to the bombing of built-up areas before entering them. Moscow’s strategy in Chechnya and Syria was to use artillery and air bombardments to pulverize cities and crush fighters’ resolve.

The UK Ministry of Defence said on Tuesday night that it believed the second city of Kharkiv was “likely encircled” by Russian forces, along with Kherson on the Black Sea, and the strategically important Sea of Azov port city, Mariupol.

In other developments:

  • Hundreds of thousands of Ukrainians have fled the fighting as a miles-long Russian military convoy north of Kyiv advances toward the city.
  • West of Kyiv, in the city of Zhytomyr, four people, including a child, were killed on Tuesday by a Russian cruise missile, a Ukrainian official said.
  • A Russian military strike in the small town of Borodjanka north-west of Kyiv on Tuesday night tore through two apartment blocks, videos on social media and confirmed by multiple news sources show.
  • Russian troops have landed in Kharkiv, according to the Security Service of Ukraine. The troops reportedly attacked a military hospital.
  • Despite the buildup of forces outside the capital, a US defence official said on Tuesday night that Russia’s move on Kyiv had stalled as its forces struggle with basic logistics challenges, including shortages of food and fuel. Some units appeared to be gripped by low morale, the official said.
  • In addition, commanders may be considering more bombardment instead of using the kind of armoured thrusts that characterised the first few days of the war, a US military thinktank said on Tuesday.

Ukraine’s defence minister, Oleksii Reznikov, said on Tuesday that the Kremlin was preparing to cut off a large part of Ukraine from the internet and communications in an effort to break local resistance.

In a highly emotional address to the European parliament on Tuesday that was greeted with a standing ovation, Ukraine’s president, Volodymyr Zelenskiy, said at least 16 children had been killed on Monday and mocked Russia’s claim that it was going after only military targets. “Where are these children, what kind of military factories do they work at? What tanks are they going at, launching cruise missiles?”

“We resist the invasive aggression,” Zelenskiy wrote on Twitter late on Tuesday, after thanking western leaders for their support. “Today, more than ever, it is important for us to feel that we are not alone.”

The United Nations says at least 136 civilians have been killed in the invasion, but that the real number of people is likely much higher.

The Russian drive to force a Ukrainian capitulation coincides with a second round of negotiations between Russian and Ukrainian officials, scheduled for Wednesday. The first round, held on the Belarus border, yielded no positive results.

Russian president Vladimir Putin has drawn global condemnation for ordering the invasion of Ukraine last Thursday, but the west has responded with sanctions that have sent the rouble to historic lows and raised the prospect of a severe recession in Russia.

The sanctions are designed to shut off Russia’s economy from the global financial system, pushing international companies to halt sales, cut ties, and dump tens of billions of dollars’ worth of investments.

The sanctions have had an immediate impact on Russia’s economy, with queues forming outside banks as Russians rush to salvage their savings.

Apple, Exxon, Ford, Nike, Boeing and Jaguar Land Rover have joined the list of multinational companies that suspended sales of their products or other operations in Russia in the wake of its invasion of Ukraine.

Ukraine, which is not a member of Nato, has called on the western military alliance to implement a no-fly zone – a request rejected by Washington, which fears stoking a direct conflict between the world’s two biggest nuclear powers.

The US, Germany, Sweden and other countries have instead sent weapons to Kyiv, and treasury secretary Janet Yellen said the United States had agreed with partners to convene a taskforce “to freeze and seize the assets of key Russian elites”.

The move “will inflict financial pain on the powerful individuals surrounding Putin and make clear that no one is beyond our collective reach,” Yellen said in a statement following a Tuesday call with Group of Seven officials.

The IMF and the World Bank condemned the Russian action in Ukraine and the “horrifying” suffering of people there, and pledged a $3bn package of support for the country in a strongly worded joint statement.