President Volodymyr Zelenskyy said protecting Ukraine's borders was a "constant priority" and that his country was ready for all possible scenarios with Russia and its ally Belarus, which Kyiv has warned could be drawn into the 10-month conflict.

Zelenskyy, in his nightly video address to Ukrainians, also issued a fresh appeal to Western nations to provide Kyiv with better air defenses as "one of the most powerful" steps to halt the Russian invasion. Early on Monday, air raid warnings again rung out over Kyiv and eastern Ukraine, with videos of blasts and air defense systems shared on social media.

"Protecting our border, both with Russia and Belarus — is our constant priority," Zelenskyy said after a meeting on Sunday of Ukraine's top military command. "We are preparing for all possible defense scenarios."