Austria's chancellor to meet Putin in Moscow as Ukraine braces for Russian assault in east

Ukraine's armed forces braced on Monday for a new Russian offensive as powerful explosions rocked cities in the south and east, while Austria's leader planned to meet Russian President Vladimir Putin and call for an end to the conflict.

Ukrainian President Volodymyr Zelensky kept up his tireless campaign to generate international support and rally his countrymen, warning the coming week would be important and tense.

"Russia will be even more afraid. It will be afraid to lose. It will fear that the truth will have to be acknowledged," Zelensky said in a late night video address.

"Russian troops will move to even larger operations in the east of our state. They may use even more missiles against us, even more air bombs. But we are preparing for their actions. We will answer."

Air raid sirens were heard across Ukraine early on Monday.

"It is likely that the enemy, in order to disrupt the supply of goods to the places of hostilities, will continue to strike at transport infrastructure facilities in Ukraine in order to destroy or disable them," the general staff of Ukraine's armed forces said.

Russian forces were continuing their offensive to establish full control over the southern city of Mariupol, seeking to storm an iron and steel plant and the seaport, it added.

Russia might also carry out provocative actions in the Transnistrian region of the Republic of Moldova in order to accuse Ukraine of aggression against a neighbouring state, the general staff said, without providing evidence.

Serhiy Gaidai, the governor of the Luhansk region in Ukraine's east, said infrastructure including food stores had been targeted by Russian "informants," also without providing evidence. Reuters could not confirm the claims.

Austrian Chancellor Karl Nehammer said he would meet Putin on Monday in Moscow for the Russian leader's first face-to-face meeting with a European Union counterpart since Russia's invasion began on Feb. 24.

"We are militarily neutral, but (have) a clear position on the Russian war of aggression against #Ukraine," Nehammer wrote of Austria on Twitter. "It must stop! It needs humanitarian corridors, ceasefire & full investigation of war crimes."

Russia's invasion has forced about a quarter of Ukraine's 44 million people from their homes, turned cities into rubble and killed or injured thousands.

It has failed to take any major cities, but Ukraine says Moscow has been gathering its forces in the east for a major offensive and has urged people to flee.

A series of powerful explosions were heard in Ukraine's northeastern city of Kharkiv and in Mykolaiv, near the Black Sea in the southern part of the country, Ukrainian media reported on Sunday.