"Initial inquiry suggests a projectile launched from the Gaza Strip landed in an open area," an army statement said, with no injuries reported.
In response, the army added, "an (Israeli) tank targeted a Hamas post in the northern Gaza Strip."
A security source from Hamas, the Gaza Strip's Islamist rulers, said two posts were targeted, causing no injuries.
The last rocket fire from Gaza into Israel occurred in October.
Since the devastating conflict of 2014, Israel and Hamas have observed a fragile ceasefire along the largely closed border.
The Israeli army usually retaliates by striking Hamas positions, which it holds responsible for the territory.