West vows more Russian sanctions as war enters new phase

The United States and allies agreed to impose more sanctions on Moscow on Tuesday as Russia pushed ahead with its new offensive targeting eastern Ukraine in the latest phase of the bloody invasion.

Russia's defence ministry said that "high-precision air-based missiles" had hit 13 Ukrainian positions in parts of Donbas while other air strikes "hit 60 military assets", including in towns close to the eastern frontline.

Ukraine's armed forces said fighting had increased throughout the east after president Volodymyr Zelensky announced Russia had kicked off the widely anticipated offensive in Ukraine's industrial heartland.

"The Russian occupiers intensified offensive operations along the entire line of contact," the general staff of Ukraine's armed forces said in a report published early Tuesday.

Russia's foreign minister Sergei Lavrov appeared to acknowledge the new offensive, stating that "another phase of this operation is beginning", during an interview with media outlet India Today.

Following the new push, the United States and European Union agreed on the need to "increasing Moscow's international isolation", during a virtual meeting between US President Joe Biden and European leaders.

"We will further tighten our sanctions against Russia and step up financial and security assistance for Ukraine," European Commission chief Ursula von der Leyen wrote on Twitter.

Separately, German chancellor Olaf Scholz called the death of thousands of Ukrainian civilians "a war crime" for which Russian President Vladimir bears responsibility.

Ahead of Russia's advance, Ukrainian authorities had urged people in Donbas to flee west to escape, even as officials called off evacuations for a third straight day from frontline cities due to ongoing fighting.

In the Donbas town of Novodruzhesk, Nadya, 65, said "we are bombed everywhere".

"It's a miracle that we're still alive," she said, her voice trembling.

"We were lying on the ground and waiting. Since February 24 we've been sleeping in the cellar."

Control of Donbas and the besieged southern port of Mariupol would allow Moscow to create a southern corridor to the Crimean peninsula that it annexed in 2014, and deprive Ukraine of much of its coastline and a major revenue resource.

Russia continued its relentless battle to capture Mariupol, as Moscow issued a fresh call for the city's defenders to surrender and announced the opening of a humanitarian corridor for Ukrainian troops who agreed to lay down their arms.

During an interview broadcast on CNN Tuesday, Pavlo Kyrylenko -- who oversees the Donetsk region's military administration -- said Mariupol remained contested.

"The Ukrainian flag is flying over the city," said Kyrylenko.

Putin has said he launched the so-called military operation in Ukraine on 24 February to save Russian speakers in Ukraine from a "genocide" carried out by a "neo-Nazi" regime.

However organisers of a ceremony marking the liberation of the Nazi Mauthausen concentration camp in Austria said Tuesday that the ambassadors of Russia and Belarus were asked not to attend as their presence would be against the surviving prisoners' wishes and their belief in peace and freedom.

While much of the focus has remained in Ukraine's east, Moscow has also targeted the country's west with air strikes, killing at least seven people in the city of Lviv near the Polish border on Monday.

Lviv has largely been spared bombardment since Russia invaded, and the city and its surroundings had become a haven for those seeking safety from the war zone.

The regional governor of the eastern Lugansk region Sergiy Gaiday said Ukrainian forces continued to hold their ground amid heavy fighting.

"We have positional battles in the cities of Rubizhne and Popasna. The enemy cannot do anything though. They are losing people and equipment there," Gaiday said.

"Our guys are shooting down drones there. Shooting down planes on the border of the Lugansk and Kharkiv regions, so they are holding on," he added.

Later Tuesday, the UN secretary-general Antonio Guterres denounced Russia's ongoing offensive as he issued calls for a four-day truce to mark Orthodox Holy Week.

"Instead of a celebration of new life, this Easter coincides with a Russian offensive in eastern Ukraine," Guterres told reporters.

"The intense concentration of forces and firepower makes this battle inevitably more violent, bloody and destructive," he said, calling for a "humanitarian pause" from Holy Thursday until Easter Sunday on 24 April.