Residents carry their belongings near buildings destroyed in the course of Ukraine-Russia conflict, in the southern port city of Mariupol, Ukraine April 10, 2022.
Residents carry their belongings near buildings destroyed in the course of Ukraine-Russia conflict, in the southern port city of Mariupol, Ukraine April 10, 2022. Reuters / ALEXANDER ERMOCHENKO

Ukraine said on Monday it expected Russia to launch a huge new offensive soon, as Moscow shifts its focus to seizing territory in the east after its invasion force was driven from the gates of Kyiv this month.

The first EU leader to meet Vladimir Putin face-to-face since the war began, Austrian Chancellor Karl Nehammer, gave a grim account of his talks with the Russian leader, held at a residence outside Moscow.

"I generally have no optimistic impression that I can report to you from this conversation with President Putin," he said. "The offensive (in eastern Ukraine) is evidently being prepared on a massive scale."

After withdrawing forces from northern Ukraine, including suburbs of Kyiv lain to waste under its occupation, Russia now says its main objective is eastern Ukraine. It is demanding Kyiv cede control of swathes of territory there, known as the Donbas, to separatist fighters. Kyiv says it is girding for a new battle.

"We forecast that active combat will begin in these areas in the nearest time," Ukraine's defence ministry spokesman Oleksandr Motuzyanyk said.

A U.S. official said Washington believed Russia was trying to reinforce and resupply its troops in the Donbas.

The biggest prize Russia aims to capture in the Donbas is Mariupol, the main eastern port, where thousands of people are believed to have died under a near-seven week siege. If Russia finally captures it, it could better link troops advancing from the east with those from Crimea, and shift their focus to a new attempt to encircle the main Ukrainian force in the east.

In his latest plea for international support, President Volodymyr Zelenskiy told South Korea's parliament there were tens of thousands of dead in Mariupol, a figure that has not been confirmed independently. "But even despite this, the Russians are not stopping their offensive", he said.

Russia was concentrating tens of thousands of troops for its new assault, Zelenskiy said.

Ukraine's military commander-in-chief, General Valeriy Zaluzhnyi, insisted Mariupol's defenders were still holding out.

"We are doing the possible and impossible for the victory and the preservation of the lives of personnel and civilians in all directions," Zaluzhniy said. "Believe in the Armed Forces of Ukraine!"

Earlier, a post on the Facebook page of a brigade of marines holding out in Mariupol said they had run out of ammunition and were now facing death or capture, with Monday likely to be the "ultimate battle". Petro Andryushchenko, an aide to the Mariupol mayor, said the page had been hacked and the post was fake. Reuters could not independently verify it.

British intelligence said Ukrainian forces had already pushed back several Russian assaults in eastern regions.

RUSSIA WOULD NOT PAUSE FIGHTING FOR TALKS

Russia would not pause the fighting for any new round of peace talks, Foreign Minister Sergei Lavrov said.

"A decision was made that during the next rounds of talks, there would be no pause (in military action) so long as a final agreement is not reached," Lavrov said.

Britain's defence ministry said Russian shelling continued in the Donetsk and Luhansk regions, which together form the Donbas. But Ukrainian forces had beaten back several assaults and destroyed Russian tanks, vehicles and artillery equipment, it said in its regular intelligence bulletin.

Russia's defence ministry said its sea-launched missiles on Sunday destroyed S-300 anti-aircraft missile systems which had been supplied to Ukraine by a European country. The systems were concealed in a hangar on the outskirts of Dnipro in central Ukraine, it said. Reuters could not confirm this.

As Russian forces have retreated from the outskirts of Kyiv they left behind evidence of Ukrainian civilians killed under their occupation, in what Western countries have condemned as war crimes. Moscow has rejected the accusations and denies targeting civilians.

Last week, Russia also killed 57 people, according to Ukrainian officials, in a missile strike on a train station in the Donetsk region, where thousands of civilians were trying to flee the expected new Russian advance. Moscow denied blame for the strike. The Russian missile that hit the station had the words "for the children" written on the side.

Luhansk Governor Serhiy Gaidai, speaking to Ukrainian television on Monday, said shelling in the region was increasing day by day.

"The most difficult situation is in Rubizhne and Popasna. They are being shelled constantly, round the clock," Gaidai said, referring to cities in the region.

He urged all civilians to evacuate.

"Those that wanted to leave have already left, while now many are left in bomb shelters who are perhaps frightened to come out of the shelters, or scared to lose their possessions."

Just outside the Donbas region, the main eastern city Kharkiv came under heavy shelling on Monday, causing multiple casualties including one child who was killed, Mayor Ihor Terekhov said in a televised interview.

Terekhov said that Ukrainian forces were focused and ready to defend the city if it comes under a new attack: "There is no panic in the city," he said.

German Foreign Minister Annalena Baerbock, speaking before a meeting of European ministers in Luxembourg, said Berlin saw "massive indications" of war crimes in Ukraine.

Several EU ministers said on Monday the bloc's executive was drafting proposals for an oil embargo on Russia, although there was still no agreement to ban Russian crude.