Explosions lit up the sky over Kyiv overnight as Russian forces seized control of the southern port city of Kherson.
Ukraine’s capital was rocked by a series of blasts in the early hours of Thursday after a huge explosion near Kyiv’s central train station.
In Kherson, the mayor said Russian troops had forced their way into the city council building and imposed a curfew on residents.
It is the first city to fall to Russian forces since they invaded eight days ago.
In other developments, the UN refugee agency said one million people have fled Ukraine since Russia’s invasion, in the swiftest exodus of refugees this century.
BREAKING 🚨 Sky glows orange after large explosion in Kyiv pic.twitter.com/ilNr5n2mcx
— Insider Paper (@TheInsiderPaper) March 3, 2022
The International Criminal Court (ICC) opened an investigation on Wednesday night after Britain and 37 allies referred Russia over what the Prime Minister described as “abhorrent” attacks.
ICC prosecutor Karim Khan said work would begin “immediately”, with his team already collecting evidence, after the co-ordinated referral freed him to get to work without the need for judicial approval.
The move came as Ukraine’s capital Kyiv braced for a siege, its second-largest city Kharkiv reeled from further strikes.
However, a massive Russian column of hundreds of tanks and other vehicles appeared to be stalled roughly 16 miles from Kyiv.
In its latest intelligence assessment, the UK Ministry of Defence said the column had been “delayed by staunch Ukrainian resistance, mechanical breakdown and congestion”.
It added: “The column has made no discernible progress in over three days.”
In his latest video address, Ukraine’s President Volodymyr Zelensky vowed resistance in the face of Russian aggression would continue.
“We are a people who broke the enemy’s plans in a week,” he said.
“These plans had taken years to write - they are mean, with hatred for our country, for our people.”
The tally from UNHCR amounts to more than two per cent of Ukraine’s population on the move in under a week. The World Bank counted the country’s population at 44 million at the end of 2020.
A second round of talks aimed at ending the fighting was expected on Thursday, but there were little hopes of a breakthrough.
Foreign Secretary Liz Truss will meet counterparts from the Baltic states of Estonia, Latvia and Lithuania as part of the UK’s effort to demonstrate support for eastern Nato allies.
The Prime Minister had spoken to Mr Zelensky on Wednesday, promising further support and weapons for the forces resisting Russia’s military and sharing his “disgust” at the Kremlin’s attacks.
Strikes that damaged the Babi Yar Holocaust memorial in Kyiv and the central square in Kharkiv have caused revulsion, and Western allies fear it is a sign of a shift in Russian tactics further towards the indiscriminate targeting of urban areas.
Moscow’s international isolation was further displayed when the UN General Assembly voted overwhelmingly to demand it immediately withdraws its military from Ukraine, with 141 nations backing the motion and only five, including alleged co-aggressor Belarus, opposing it.
For the first time the UK explicitly accused Mr Putin of war crimes, with Downing Street claiming “horrific acts” were occurring on an almost hourly basis as population centres are targeted.
At Prime Minister’s Questions, Mr Johnson said: “Putin has gravely miscalculated; in his abhorrent assault on a sovereign nation, he has underestimated the extraordinary fortitude of the Ukrainian people and the unity and resolve of the free world in standing up to his barbarism.”
He added: “What we have seen already from Vladimir Putin’s regime in the use of the munitions that they have already been dropping on innocent civilians, in my view, already fully qualifies as a war crime.”
More than 2,000 civilians have died since the invasion began, Ukraine’s state emergency service said, although that figure has not been independently verified.