Ukraine and Russia: What you need to know right now

* Russian-backed separatists said five soldiers from the Azovstal steel plant had surrendered after a Russian ultimatum on Wednesday, a day after Russia said no-one had responded to a similar call. * Russia said it had test-launched its Sarmat intercontinental ballistic missile, a new addition to its nuclear arsenal which President Vladimir Putin said Moscow's enemies will not be able to match.

A Russian ultimatum to Ukrainian troops in Mariupol to surrender or die expired on Wednesday afternoon with no mass capitulation, but the commander of a unit believed to be holding out in the besieged city said his forces could survive just days or hours. More than five million people have now fled Ukraine, the United Nations refugee agency said.

WIDER IMPACT * World Bank President David Malpass said the food security crisis resulting from the Ukraine conflict was expected to last months and perhaps into next year.

* U.S. and Chinese defence chiefs spoke in a rare phone call, both sides said. Beijing said Washington must not use the Ukraine conflict to smear and threaten China. * President Joe Biden will host U.S. military leaders in an annual gathering that takes on extra significance as the war enters a risky new phase. Biden, British Prime Minister Boris Johnson and Canadian Prime Minister Justin Trudeau have pledged to send more artillery weaponry to Ukraine.

* Ukraine called on the Red Cross to establish contact with what it said were 500,000 people deported from Ukraine to Russia. * President Vladimir Putin called for structural changes in Russia's metallurgical industry to counter Western sanctions he said were starving it of some components and restricting its ability to sell some goods abroad.

* Western nations are preparing to stage coordinated walk-outs to protest Russia's invasion of Ukraine at Wednesday's meeting of G20 finance ministers in Washington. FIGHTING

* Russia is still building up its military presence on Ukraine's eastern border and fighting in the southeastern Donbas region is intensifying as Russian forces seek to break through Ukrainian defences, a British military update said. * Russian-backed separatists said five soldiers from the Azovstal steel plant had surrendered after a Russian ultimatum on Wednesday, a day after Russia said no-one had responded to a similar call.

* Russia said it had test-launched its Sarmat intercontinental ballistic missile, a new addition to its nuclear arsenal which President Vladimir Putin said Moscow's enemies will not be able to match. * President Volodymyr Zelenskiy said an estimated 1,000 civilians were sheltering at the Azovstal steel plant in Mariupol and he was ready to swap Russian prisoners in exchange for safe passage for the trapped civilians and Ukrainian soldiers.

QUOTES * "I never thought that someday I will live in a castle," said Maria Nazarchuk, 20, an accountancy student among 11 Ukrainians staying in medieval castle in the west of Ireland.

(Compiled by Himani Sarkar, Philippa Fletcher and Tomasz Janowski)