Ukraine pleaded for more weapons from the West to help it end the siege of Mariupol and fend off an expected Russian offensive in the east, as more reports emerged of rape and brutality against Ukrainian civilians by Russian forces.

Ukrainian President Volodymyr Zelenskiy said in a televised address late on Monday that Russia could resort to chemical weapons as it amassed troops in the eastern Donbas region for a new assault on the port of Mariupol, where thousands are believed to have died under a near-seven week siege.

“When it comes to the necessary weapons, we still depend on supplies, on our partners. Unfortunately, we are not getting as much as we need to end this war faster ... In particular, to lift the blockade of Mariupol," he said.

The first European Union leader to meet Russian...