After Moscow suffered some of its heaviest losses earlier this week, Ukraine says it is hopeful it will soon be able to make "deep strikes" into mainland Russia.

Ukrainian Foreign Minister Andrii Sybiha said on Wednesday he was "cautiously optimistic" after discussing with U.S. Secretary of State Antony Blinken the possibility of conducting deep strikes on Russia as well as Euro-Atlantic integration.

The attack ended a two-month pause in missile strikes on Kyiv, which had only been hit by Russian drones during that period.

Russia struck Kyiv with a sophisticated missile and drone attack for the first time in 73 days on Wednesday morning and damage is still being assessed, a top official in the Ukrainian capital said. Air raid warnings blared for hours.

The U.S. says there will be a "firm response" as Ukrainian forces holding ground in Russia's Kursk region now face North Korean troops "engaging in combat."

Russia attacked the Ukrainian capital Kyiv with a sophisticated combination of missiles and drones for the first time in 73 days on Wednesday, authorities reported, as the Pentagon said most of the North Korean troops sent to help Moscow’s war effort are fighting to drive Ukraine’s army off Russian soil in the Kursk border region.