Ukraine said Russia had started an anticipated new offensive in the east of the country, with explosions reported all along the front lines as well as attacks in other regions.

Ukrainian President Volodymyr Zelenskiy said Russia had begun the "Battle of Donbas" in the east on Monday and a "very large part of the entire Russian army is now focused on this offensive."

"No matter how many Russian troops they send there, we will fight. We will defend ourselves," he vowed in a video address.

Zelenskiy's chief of staff Andriy Yermak called it "the second phase of the war" and assured Ukrainians that their forces could hold off the offensive. "Believe in our army, it is very strong," he said.

Ukrainian media reported...