The morning after President Biden accused Russia of fabricating a crisis in Ukraine as a pretext for an all-out assault on the nation, leaders of Russia-backed separatists in eastern Ukraine issued a call on Saturday for all men in the territory they control to register to fight.

That came one day after the separatists, who are loyal to Moscow and viewed by the West as its proxies, called for 700,000 women and children to evacuate the region, claiming that Ukrainian government forces were planning a large-scale attack. The Kiev government denied any such intent, and the US dismissed the accusation as a lie designed to give Russia a pretext for launching an invasion.

Biden said on Friday that he was “convinced” that President Vladimir V. Putin of Russia had decided to invade Ukraine in the coming days, citing classified US intelligence and the positioning of large numbers of Russian soldiers along Ukraine’s borders.

The heightened sense of urgency expressed by Washington was not immediately apparent in Kiev, despite Biden’s having explicitly identified the city as a Russian target.

“Russia will do something,” Sofiya Soyedka, a 32-year-old Kiev resident, said just after Biden’s dire warning on Friday. But invade Kiev? “No way,” she said.