Live: Next 24 Hours Crucial for Ukraine, Zelenskiy Tells UK's Johnson

Ukraine's President Volodymyr Zelenskiy told UK Prime Minister Boris Johnson by telephone on Sunday that the next 24 hours are crucial for Ukraine, a Downing Street spokesperson said, reports Agencies.

Johnson said the UK and its allies would do everything possible to guarantee that defensive aid reached Ukraine, the spokesperson said in a statement.

Ukraine vows no 'capitulation' at talks

Ukraine vowed not to give ground at talks with Moscow on Sunday as Ukrainian forces resisted a Russian invasion four days in and Moscow put its nuclear forces on high alert.

Ukraine said it had agreed to send a delegation to meet Russian representatives on the border with Belarus, which has allowed Russian troops passage to attack Ukraine.

But Kyiv insisted there were no pre-conditions to the talks.

"We will not capitulate, we will not give up a single inch of our territory," Ukrainian Foreign Minister Dmytro Kuleba said ahead of the first public contact between the two sides since war erupted.

Ukraine's President Volodymyr Zelensky was sceptical.

"As always: I do not really believe in the outcome of this meeting, but let them try," he said.

The UN General Assembly will hold a rare emergency session Monday to discuss the conflict.

Europe and Canada move to close skies to Russian planes

European nations and Canada moved on Sunday to shut their airspace to Russian aircraft.

Aeroflot said it would cancel all flights to European destinations after EU foreign policy chief Josep Borrell said the European Union had decided to close its airspace to Russian traffic.

The United States is considering similar action, but has yet to make a final decision, according to US officials.

Germany, Spain and France joined Britain, the Nordics and Baltic states in declaring bans on Russian use of their airspace, a major escalation in a tactic by mostly NATO allies to wage economic war against Putin in retaliation for the invasion.

Australia to send lethal weapons to Ukraine

Australia will provide lethal military equipment to Ukraine to help the Ukrainians resist the Russian invasion.

The Australian government's announcement Monday gave no details on what material it may be sending. The move follows an offer on Friday of non-lethal military equipment, medical supplies and a $3 million contribution to a NATO trust fund for the support of the besieged country.

Russian convoy of ground forces, tanks moving toward Kyiv

Satellite imagery taken on Sunday showed a large deployment of Russian ground forces including tanks moving in the direction of the Ukrainian capital Kyiv from approximately 40 miles (64 km) away, a private US company said.

The images released by Maxar Technologies Inc showed a deployment comprised of hundreds of military vehicles and extending more than 3.25 miles (5 km), Maxar said.

The convey was situated northeast of the Ukrainian city of Ivankiv and contained fuel, logistics and armoured vehicles including tanks, infantry fighting vehicles and self-propelled artillery, it said.

Putin puts nuclear forces on alert

The United States and Germany slam Russian President Vladimir Putin for putting his nuclear forces on alert, saying he was again "manufacturing threats that don't exist" because his invasion of Ukraine "has been halted".

Russian army having problems

Russia's invasion force has lost momentum and is having logistical and supply problems after facing stiff Ukrainian resistance, the White House claims.

US officials say it has failed to gain air superiority as Moscow admits to killed and injured soldiers.

Driven from Kharkiv

Ukraine claims to have expelled Russian troops from its second city Kharkiv in the east of the country after Russian armoured vehicles got through its defences.

Kyiv holds out

Ukraine says it is holding the line around the capital Kyiv but was fighting Russian "sabotage groups" that had infiltrated the city.

Talks near Chernobyl

Ukraine agrees to hold talks with Russia at its border with Belarus -- near the Chernobyl exclusion zone -- after a call between President Volodymyr Zelensky and Belarus leader Alexander Lukashenko.

Kremlin's 'big push'

The talks come as Russia orders an advance "from all directions". It claims to have besieged the southern cities of Kherson close to Crimea and Berdyansk on the Sea of Azov.