Follow developments at the UN General Assembly as they happen.

Members of the UN Security Council assailed Russia on Thursday for its war in Ukraine, denouncing Moscow's actions since its invasion seven months ago that have included “indiscriminate” attacks on civilians and acts of “horrific” sexual violence.

Russian Foreign Minister Sergey Lavrov walked out of the 15-member chamber after delivering a series of unfounded claims, including that the discovery of more than 450 bodies in Bucha was “staged”.

He also doubled down on Russian President Vladimir Putin’s allegations that the Ukrainian government endorses “Nazism” and accused Kyiv of “Russophobia” by suppressing the rights of Russian-speaking people.

“We have no illusions that today the armed forces of Russia and the militias of Lugansk and Donetsk are being opposed not only by the neo-Nazi formations in the Kyiv regime but the military machine of the collective West,” Mr Lavrov said.

US Secretary of State Antony Blinken said Mr Putin should be held to account over what has happened in Ukraine.

“The very international order we've gathered here to uphold is being shredded before our eyes,” Mr Blinken told the Security Council in a special session as leaders met at the UN General Assembly in New York.

“We cannot — we will not — let President Putin get away with it,” he said.

The top US diplomat said it was critical to show that “no nation can redraw the borders of another by force”.

Britain's Foreign Secretary James Cleverly said that in parts of Ukraine currently under Russian control, civilians are subjected to torture, arbitrary detention, and forced deportation to Russia.

“President Putin’s war has spread hardship and food insecurity across the globe plunging millions of the world’s most vulnerable into hunger and famine,” Mr Cleverly said.

“And once again, as we’ve seen here today, Russia has sought to deny responsibility.”

Mr Lavrov used his speech to criticise the West for its role in the conflict, during which US and European nations have sent billions of dollars of sophisticated weaponry into Ukraine that has been used to kill thousands of Russian soldiers.

“Intentional fomenting of this conflict by the collective West remains unpunished — of course, you won't punish yourself,” Mr Lavrov said.

Ukrainian Foreign Minister Dmytro Kuleba accused Russia of spreading a “torrent of lies” and urged allied nations to hold fast in their support of Ukraine.

“We must stay united to stop Russia's blackmail and the war on humanity,” he said.

The council meeting comes after Mr Putin called up 300,000 reserve troops and reiterated nuclear threats, saying Russia is prepared to use “all the means at our disposal” to defend itself.

Karim Khan, prosecutor for the International Criminal Courts, spoke to the Security Council about the suffering he has seen in Ukraine during his three trips there since the February 24 invasion.

“When I went to Bucha and went behind St Andrew's Church, the bodies I saw were not fake,” he said. “When I walked the streets of Borodyanka the destruction that I saw of buildings and schools was all too real.”

Mr Khan said his team was still gathering evidence and engaged in “sometimes very painstaking work to grapple with the facts, to separate truth from fiction and to build a picture of what actually happened”.

Before the war, Russia had forged closer ties with China, but the US has welcomed what it sees as a cautious tone from Beijing, which has not sent significant military supplies to Moscow.

“The priority is for the parties to resume dialogue without preconditions,” Chinese Foreign Minister Wang Yi told the Security Council.