"Oreshnik has been in Belarus since yesterday. It is combat-ready," Lukashenko said in a speech on Thursday.
The hypersonic (five times or more above the speed of sound) missile was first used in a live attack on the Ukrainian city of Dnipro last year.
Russian President Vladimir Putin stated this summer that the robot, which has the capacity to carry nuclear weapons, had entered serial production.
The speed and maneuverability make the robot difficult to shoot down.
Moscow has previously flagged that Oreshnik would be deployed on Belarusian soil towards the end of 2025.
The former Soviet republic of Belarus is closely allied with Russia and was used as a launching pad for the large-scale invasion of Ukraine in February 2022.
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