Around 20,000 people have fled Mariupol in what is believed to be the biggest evacuation yet from the besieged port city.
Around 570 of some 4,000 vehicles that left the city have reached Zaporizhzhia which is 160 miles (260km) northwest while others will spend the night in various towns along the way.
And while talks between Russian and Ukrainian representatives have become “more constructive”, the bombardment of Kyiv has been stepped up, with attacks on apartments and a subway station.
President Volodymyr Zelenskyy’s senior adviser described the talks as a “very difficult and viscous negotiation process”.
“There are fundamental contradictions. But there is certainly room for compromise. During the break, work in subgroups will be continued,” he added.
Kyiv says ‘definitely room for compromise’ in talks amid NATO concession hint – latest updates on Ukraine
With the number of people driven from the country by the war eclipsing three million, large explosions thundered across the capital before dawn from what Ukrainian authorities said were artillery strikes.
Mayor Vitali Klitschko has brought in a curfew until 7am on Thursday (5am GMT).
People will only be able to move around the city with “special permission” except to “go to bomb shelters”, the mayor said.
In other developments:
• More than 100,000 Britons register interest to house Ukrainian refugees
• UK announces sanctions against 370 more Russian nationals and entities
• UK bans luxury goods exports to Russia and hikes import tariffs on products – including vodka
• Briton who travelled to warzone to join military fight against Russia leaves over ‘suicide mission’ fears
• Employee interrupts Russian news programme with anti-war slogan
“The capital is the heart of Ukraine, and it will be defended. Kyiv, which is currently the symbol and forward operating base of Europe’s freedom and security, will not be given up by us,” he added.
Five people were killed in air strikes targeting Kyiv early on Tuesday morning, President Volodymyr Zelenskyy said, adding that some humanitarian corridors had been partially opened.
“Everyone is angry,” Mr Klitschko told Sky News correspondent Alex Crawford.
He has been talking to residents and “they don’t want to leave, (they) want to defend our city”, he said.
“They’re really upset about what Russian soldiers are doing to civilians.”
People are asking about weapons and want to join civil defence forces to protect their homes, he added.
His brother, Wladimir Klitschko, said Russian troops are so close you can “throw a stone” at them, adding: “I’m not even kidding.”
His frustration with the reaction of the West was clear, describing it as a “policy of waiting and looking”.
He said. “Wake up, guys. It’s a wake up call and it’s been called for the past 20 days and you must act now. If you hesitate, hesitation is considering to be dead. Isolate Russia. Stop this War.”
The prime ministers of Poland, Czech Republic and Slovenia travelled to Kyiv on Tuesday in a show of support for Ukraine.
The three leaders went ahead with the hours-long train trip despite worries within the European Union about the security risks of traveling within a war zone.
Poland’s Mateusz Morawiecki said on social media: “It is here, in war-torn Kyiv, that history is being made.
“It is here, that freedom fights against the world of tyranny. It is here that the future of us all hangs in the balance,” Morawiecki said on Twitter.
Every second, another child becomes a refugee
Of the three millions who have fled the country, more than 1.8 million of them travelled to Poland, the UNHCR said, with spokesman Matthew Saltmarsh adding that 300,000 had moved on from there to western Europe.
On Tuesday, a total of around 29,000 people were evacuated from Ukrainian cities through humanitarian corridors, most of them leaving the besieged port of Mariupol.
And on average, on each of the last 20 days, 73,000 Ukrainian children have become refugees, Unicef has said.
That is about 51 a minute – almost one every second.
The Red Cross has confirmed more than 100 buses carrying civilians have left the besieged city of Sumy in northeastern
A spokesman said they were heading towards Poltava, in central Ukraine, adding that the Russian side had given a green light for the evacuation.
A new attempt will be made to deliver supplies to Mariupol. The city council said 2,000 cars had been able to leave on Tuesday.
People trapped there by Russian shelling are “essentially being suffocated with no aid”, Mr Watson said.
The mayor of Kharkiv says more than 600 buildings in the city have now been destroyed by Russian shelling.
He also said anyone who wants to leave still can do by train or road.
Russia attempting to subvert Ukrainian democracy – MoD
In an update on Tuesday morning, the UK’s Ministry of Defence (MoD) said it appeared Russia was trying to “consolidate political control” of Ukraine.
According to reports, Moscow may be seeking to “stage a ‘referendum’ in Kherson” in an attempt to “legitimise the area as a ‘breakaway republic’ similar to Donetsk, Luhansk and Crimea”, the MoD said in its latest intelligence update.
There have been “multiple demonstrations” over “several days” in the “Russian occupied” Ukrainian cities of Kherson, Melitopol and Berdyansk, it added.
“Further protests were reported in (Kherson) yesterday with Russian soldiers reportedly firing warning shots in an attempt to disperse peaceful protesters.”
The MoD said Russia had reportedly installed its own mayor in Melitopol following the alleged abduction of his predecessor on Friday, and that the mayor of Dniprorudne had also reportedly been abducted by Russian forces.
“Russia is likely to make further attempts to subvert Ukrainian democracy as it attempts to consolidate political control of Ukraine,” it concluded.
Foreign Office minister James Cleverly told Sky News: “A faux election to try to justify Russia’s aggression to Ukraine will be recognised for exactly what it is, and that is a fake.”
Russia’s defence ministry said on Tuesday morning that its forces had taken control of all territory in the Kherson region, Russian news agencies reported.
Peace talks ‘pretty good’
President Zelenskyy, in his nightly address, said he wanted a “fair peace”.
“Our delegation also worked on this in negotiations with the Russian party. Pretty good, as I was told. But let’s see. They will continue tomorrow.”
Ukraine’s president also issued a stark choice to Russian troops, telling them that if they continue to attack his country: “Your life will be taken.”
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In a possible reference to a TV employee who held an anti-war sign live on air, Mr Zelenskyy said he was “grateful to those Russians who do not stop trying to convey the truth – to those who fight disinformation and tell the truth”.
Following a court hearing, Marina Ovsyannikova was fined 30,000 roubles (£213), according to state media.