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.

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 * Top finance officials from Britain, the United States and Canada walked out of Wednesday's meeting of finance officials from the world's top 20 economies as Russian representatives spoke.

* 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. * 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. FIGHTING

* Russia's military buildup on Ukraine's eastern border continues and fighting in the southeastern Donbas region is intensifying, 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. * 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. * Ukraine's deputy prime minister said an agreed humanitarian corridor to evacuate civilians from Azovstal had not worked as planned, blaming Russian forces for not holding their ceasefire.

QUOTES * "This truly unique weapon will strengthen the combat potential of our armed forces, reliably ensure Russia's security from external threats and provide food for thought for those who, in the heat of frenzied aggressive rhetoric, try to threaten our country," President Putin said about Sarmat missile after its first test launch.

(Compiled by Philippa Fletcher and Tomasz Janowski)