Russia unveiled the weapon last year after using it to strike the Ukrainian city of Dnipro, in an escalation during the conflict, now nearing its fourth anniversary.

Moscow had already deployed tactical nuclear weapons in Belarus in 2023 and said it could station Oreshnik there by the end of 2025.

"Oreshnik has been in Belarus since yesterday. And it's going on combat duty," Lukashenko said in his annual speech.

Belarus, a former Soviet republic, is a key Russian ally. Moscow used Belarusian territory to launch its offensive against Ukraine in February 2022.

In August, Minsk said it would practice the deployment of Oreshnik missiles during the joint Zapad-2025 ("West-2025") drills close to the EU and NATO's eastern flank border.