Only four buses with civilians managed to escape from Mariupol after several unsuccessful attempts, Ukrainian officials said on Thursday, as thousands more remained trapped under relentless Russian attacks against the last pockets of Ukrainian resistance in the devastated southern port city.
Another attempt to evacuate civilians from Mariupol will be made on Thursday, Ukraine's Deputy Prime Minister Iryna Vereshchuk said.
In Kyiv, Spain's Prime Minister Pedro Sánchez and Denmark's Mette Frederiksen became the latest European leaders to show support with a visit to the capital.
They were due to meet with President Volodymyr Zelenskyy, who warned in a video address overnight that the Russians were not "abandoning their attempts to score at least some victory by launching a new, large-scale offensive".
"The West stands together to support the Ukrainian people," Danish Prime minister Frederiksen said in a statement.
Meanwhile, the Kremlin said it submitted a draft of its demands for ending the war, and the West raced to supply Ukraine with heavier weapons to counter the Russians' new drive to seize the industrial east.
Britain's Defence Ministry said in an assessment that Russia likely desires to demonstrate significant successes ahead of its annual May 9 Victory Day celebrations.
"This could affect how quickly and forcefully they attempt to conduct operations in the run-up to this date."
As fears grew for the fate of civilians in Mariupol, the Kyiv regional police said on Thursday that two mass graves with nine bodies were discovered in the city of Borodyanka, northwest of the capital.
The findings added to thousands of civilians reported killed by Russian forces, who have been accused of wholesale abuses of Ukrainians.
Head of the Kyiv regional police Andriy Nebytov said two women and a teenager were among the "civilians killed by the Russian occupiers".
"I want to stress that these people are civilians. The Russian military deliberately shot civilians that didn't put up any resistance and didn't pose any threat," Nebytov said, adding that some of the victims were apparently tortured.
With global tensions running high, Russia reported the first successful test launch of a new type of intercontinental ballistic missile, the Sarmat.
President Vladimir Putin boasted that it can overcome any missile defence system and make those who threaten Russia "think twice".
The head of the Russian state aerospace agency called the launch out of northern Russia "a present to NATO".
The Pentagon described the test as "routine" and said it wasn't considered a threat.
On the battlefield, Ukraine said Moscow continued to mount assaults across the east, probing for weak points in Ukrainian defensive lines.
Russia said it launched hundreds of missile and air attacks on targets that included concentrations of troops and vehicles.
The Kremlin's stated goal is the capture of the Donbas, the mostly Russian-speaking eastern region that is home to coal mines, metal plants and heavy-equipment factories.
Detaching it from the rest of Ukraine would give Putin a badly needed victory two months into the war, after the botched attempt to storm capital Kyiv.
The UK Defence Ministry said Russian forces were advancing from staging areas in the Donbas toward Kramatorsk, which continues to suffer from persistent rocket attacks.
The Luhansk governor said Russian forces control 80 per cent of his region, which is one of two that make up the Donbas.
Before Russia invaded on February 24, the Kyiv government controlled 60 per cent of the Luhansk region.
Governor Serhiy Haidai said the Russians, after seizing the small city of Kreminna, are now threatening the cities of Rubizhne and Popasna. He urged all residents to evacuate immediately.
"The occupiers control only parts of these cities, unable to break through to the centres," Haidai said on the messaging app Telegram.
Analysts have said the offensive in the east could become a war of attrition as Russia faces Ukraine's most experienced, battle-hardened troops, who have fought pro-Moscow separatists in the Donbas for eight years.
Russia said it presented Ukraine with a draft document outlining its demands for ending the conflict - days after Putin said the talks were at a "dead end".