Russian forces tightened the noose around the defenders holed up Wednesday in a mammoth steel plant that represented the last known Ukrainian stronghold in Mariupol, as a fighter apparently on the inside pleaded on a video for help: “We may have only a few days or hours left.”

With the holdouts coming under punishing new bombing attacks, another attempt to evacuate civilians trapped in the pulverized port city failed because of continued fighting.

Meanwhile, the number of people fleeing the country topped 5 million, the Kremlin said it submitted a draft of its demands for ending the war, and the West raced to supply Ukraine with heavier weapons to counter the Russians’ new drive to seize the industrial east.