CNN  — 

Poland will deploy more troops at the border with Belarus after it accused Minsk of violating its airspace, raising tensions between the NATO member and a key Kremlin ally in an increasingly volatile security landscape in Europe.

Warsaw said two Belarusian helicopters allegedly violated the Polish airspace during training exercises on Tuesday, which the Belarusian defense ministry vehemently denied and dismissed as “far-fetched.”

This came amid increased activity near a thin strip of land between Poland and Lithuania, known as the Suwalki gap or corridor, which troops from the Russian mercenary group Wagner are moving toward in an apparent attempt to increase pressure on NATO and EU members.

Belarusian leader Alexander Lukashenko brokered a deal to cap Wagner’s failed rebellion against Moscow, after which thousands of mercenary fighters were reportedly sent to Belarus.