All of Ukraine was under air alerts as of 0200 GMT after the country's air force warned of an attack including on regions bordering Poland, forcing the NATO-member to scramble aircraft to ensure air safety.

Ukrainian President Volodymyr Zelenskyy called for "sufficient pressure on Russia" after a day of missile and drone strikes killed at least 23 people.

The death toll from a Russian missile strike in the central Ukrainian city of Kryvyi Rih has risen to 18, including nine children, regional governor Serhii Lysak said.