The projectile that landed in the eastern Polish village of Przewodow on Tuesday was "Russian-produced," according to the Polish Foreign Ministry.
Reuters reporter Tommy Lund tweeted on Tuesday evening:
"POLISH FOREIGN MINIISTRY SAYS RUSSIAN-PRODUCED ROCKET FELL ON POLISH VILLAGE PRZEWODÓW AT 1540 LOCAL TIME -rtrs"
Two people were killed in an explosion in Przewodow, a village in eastern Poland about 6 kilometers (3-1/2 miles) from the border with Ukraine, firefighters said. Media reports said the strike hit a grain-drying facility.
Members of the North Atlantic Treaty Organization (NATO) are committed to collective defense, so a Russian strike on Poland could risk widening the conflict between Russia and Ukraine, which began with Moscow's invasion in February.
A NATO official said the alliance was looking into the report and was closely coordinating with Poland.
Reuters contributed.