Russia hit Kyiv with cruise missile strikes in a menacing display of defiance while the UN secretary general was visiting the city and a few hours after Joe Biden had announced a doubling of US military and economic aid to Ukraine.

Ukrainian President Volodymyr Zelenskiy said the strikes happened “immediately after” his talks with the UN chief, António Guterres, “and this says a lot about Russia’s true attitude to global institutions, about the efforts of the Russian leadership to humiliate the UN and everything that the organization represents.

“Therefore, it requires a strong response,” Zelenskiy added.

The number of casualties was not immediately clear. One of the missiles hit a residential building near to the empty Artem defense plant, which was evacuated before the 24 February invasion.

“We are still in shock. We were in the house when they bombed the building,” Maksym Maksymov, 29, a sales manager, told the Guardian. “We heard the first strike. And the then a second missile hit the building.”

Guterres said he was shocked by the missile strikes, “not because I’m here but because Kyiv is a sacred city for Ukrainians and Russians alike”.

In his nightly address, Zelenskiy said the missile strikes on Kyiv and other cities “prove that we cannot let our guard down”.

He thanked the US for the proposed new funding saying that prompt weapons supplies were “salvation not only for our people – this is salvation for all of you – for all of Europe”.

The strikes came hours after Biden asked Congress to give immediate approval for spending that would include over $33bn in military aid, involving everything from heavy artillery and armoured vehicles to greater intelligence sharing, cyberwarfare tools and many more anti-tank and anti-aircraft missiles.

Biden also requested $8.5bn in economic aid to Kyiv and $3bn in humanitarian relief, as well as funds to help increase US production of food crops and strategic minerals to offset the impact of the war in Ukraine on global supplies.

The total of $33bn is more than twice the last supplemental request approved by Congress in March and dwarfs the entire defense budget of Ukraine and of many other countries. The US president said it was aimed at helping Ukraine repel the renewed Russian offensives in the east and south of the country, but also to transition to assuring the nation’s longer-term security needs.

On the same day, Congress agreed to update the 1941 lend-lease legislation with which Franklin D Roosevelt sought to help Britain and other allies fight Nazi Germany. The updated law is intended to make it easier for the US to provide military equipment to Ukraine.

It comes in the face of Russian warnings that increased western weapons supplies to Ukraine would endanger European security, that western intervention could bring instant Russian reprisals and raise the risk of nuclear conflict.

Making the case for western aid, Biden argued that on the contrary, if Putin was not stopped in Ukraine he would continue to threaten global peace and stability.

The president framed the request principally in terms of defending Ukraine, and did not explicitly repeat the declaration earlier this week by his defence secretary, Lloyd Austin, that one of US aims in Ukraine was to weaken Russia to stop it attacking other countries.

“Despite the disturbing rhetoric coming out of the Kremlin, the facts are plain for everybody to see. We’re not attacking Russia. We’re helping Ukraine defend itself against Russian aggression,” Biden said. But he added the cost involved was “a small price to pay to punish Russia and aggression, to lessen the risk of future conflicts”.

“Throughout our history, we’ve learned that when dictators do not pay the price for their aggression, they cause more chaos and engage in more aggression,” he said. “The threats to America and the world keep rising. We can’t let this happen.”

The new military assistance the congressional funding will finance will include:

• More artillery and armored vehicles, as well as anti-tank missiles and anti-aircraft systems.

• Help to build up Ukraine’s cyberwarfare capabilities.

• More intelligence sharing.

• Support to increase Ukraine’s ability to produce munitions and strategic minerals.

• Assistance in clearing landmines and other explosives and in Ukraine’s defence against chemical, biological and dirty bomb attacks.

• A further buildup in the US military presence on Nato’s eastern flank.

The Kremlin’s official spokesperson, Dmitry Peskov, warned on Thursday that an increased western supply of heavy weapons to Kyiv would endanger European security.

“The tendency to pump weapons, including heavy weapons, into Ukraine, these are the actions that threaten the security of the continent, provoke instability,” Peskov said.

The day before, Vladimir Putin had threatened a “lightning fast” response to western intervention in Ukraine, adding: “We have all the weapons we need for this.”

His foreign minister, Sergei Lavrov, has accused the US and its allies of fighting a proxy war in Ukraine and warned of the rising danger of a nuclear conflict.

Biden rejected the accusation he was fighting a proxy war, describing the claim as part of the Kremlin’s domestic propaganda to explain the inability of Russian forces to achieve their goals.

“I think it’s more of a reflection, not of the truth, but of their failure,” the president said. He added: “No one should be making idle comments about the use of nuclear weapons.”

The package of proposals the administration is sending to Congress also includes measures to strengthen the hand of the justice department in pursuing Kremlin-aligned oligarchs seizing their assets and using the proceeds to support the war effort in Ukraine.

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Biden made his announcement as the UN secretary general was visiting Ukraine, where he described the war as “an absurdity” in the 21st century.

Guterres was touring Borodianka on Thursday, where Russian forces are accused of massacring civilians before their withdrawal, on his first visit to Ukraine since the start of the invasion on 24 February, before talks with President Volodymyr Zelenskiy.

In nearby Bucha, where dozens of civilian bodies, some with their hands tied, were discovered this month, Guterres backed an investigation by the international criminal court into possible war crimes in Ukraine. “I appeal to the Russian Federation to accept, to cooperate with the ICC,” he said.

Ukraine’s prosecutor general Iryna Venediktova named 10 Russian soldiers allegedly involved in human rights abuses during the month-long occupation of Bucha.

Venediktova also told German TV that that Ukrainian investigators had identified “more than 8,000 cases” of suspected war crimes since Russia’s invasion.