The military says that Israeli tanks opened fire on targets in Syria on Monday after the mortar round landed in an open area in the Israeli-controlled Golan Heights.
Israeli military officials say "Syrian mobile artillery" was hit. The officials, speaking on condition of anonymity under military guidelines, gave no further details.
The incident marked the second straight day that Israel has responded to fire from Syria.
The mortars are believed to be coming from fighting in Syria's civil war, and Israel says the shells do not appear to be aimed at Israeli targets. Nonetheless, Israel has promised a tough response if the fire continues.