"For national security reasons, we will close the border with Belarus, including railway crossings, in connection with the Zapad manoeuvres on Thursday at midnight," Tusk told reporters.

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

The Zapad-2025 (West-2025) drills are set to take place from September 12 to 16.

In response to the joint drills, Polish and allied forces will hold their own military exercises in Poland, Tusk added. An estimated 30,000 soldiers are expected to take part.

According to the Polish premier, the Zapad war games are designed to stimulate the occupation of the "Suwalki Corridor", which stretches along the border between Poland and Lithuania, flanked by Belarus and the Russian enclave of Kaliningrad.

The corridor is often considered a "fragile spot" for NATO and could potentially be the first target of a hypothetical Russian attack.

Minsk previously stated in August that the Zapad drills would involve Oreshnik missile and nuclear strike training.

Kiev and several eastern European countries fear a possible military build-up in Belarus, which borders Ukraine, Poland, Lithuania, and Latvia.

Lithuania closed its airspace along parts of its border with Belarus at the end of August after military drones violated its airspace twice the previous month, and due to the scheduled Russian-Belarusian exercises.