A Ukrainian city far from the frontline grieved for its dead and cleared its streets on Friday, a day after a Russian missile attack killed at least 23 people and wounded scores.

Russia flattened part of an apartment building while residents slept on Friday in missile attacks near Ukraine's Black Sea port of Odesa that authorities say killed at least 21 people, hours after Russian troops abandoned a nearby outpost at Snake Island

The war in Ukraine could last for years, the head of Nato said on Sunday, as Russia stepped up its assaults after the European Union recommended that Kyiv become a candidate to join the bloc.

Ukraine said on Tuesday its forces were still holding out inside Sievierodonetsk and trying to evacuate civilians, after Russia destroyed the last bridge to the devastated eastern city in a potential turning point in one of the war's bloodiest battles.

At least five people died following strikes on civilian infrastructure in Ukraine's separatist-controlled city of Donetsk, Russian investigators said Monday, claiming the attack was carried out by Kyiv's forces.

Russian forces were launching an all-out assault to encircle Ukrainian troops in twin cities straddling a river in eastern Ukraine on Tuesday, a battle which could determine the success or failure of Moscow's main campaign in the east.

Ukraine ruled out a ceasefire or concessions to Moscow while Russia intensified an offensive in the eastern Donbas region and stopped sending gas to Finland in its latest salvo in response to Western sanctions and its deepening international isolation

Russia's defence ministry said on Friday that the first phase of its military operation in Ukraine was mostly complete and that it would focus on completely "liberating" eastern Ukraine's Donbass region.

US President Joe Biden landed in Rzeszow, Poland, on Friday to get a firsthand look at international efforts to help some of the millions of Ukrainian refugees fleeing war in their country, and speak to American troops bolstering Nato's eastern flank.

Officials in Central Europe voiced concern on Sunday that they were reaching capacity to comfortably house some of the nearly 3.5 million refugees who have fled Ukraine since Russia's invasion and are now camped in temporary accommodation.

More than 3.3 million refugees have now fled Ukraine since the Russian invasion, the United Nations said Saturday, while nearly 6.5 million are thought to be internally displaced within the country.

President Volodymyr Zelenskiy called on Saturday for comprehensive peace talks with Moscow to stop its invasion of Ukraine, saying it would otherwise take Russia "several generations" to recover from its losses in the war.