Israeli warplanes hit Hamas targets in the Gaza Strip early on Monday after a rocket fired by Palestinians slammed into southern Israel, the army said.
It did not elaborate on the targets but Palestinian security sources said several missiles were fired at farmland east of Rafah in the south of the coastal enclave.
Israeli "fighter jets targeted underground infrastructure in the southern Gaza Strip, in response to the projectile that was launched at Israel earlier," an army statement said.
No casualties were reported in either incident.
The strikes followed fierce exchanges over the weekend in which Israeli ground forces killed two Palestinian teenagers in the enclave in cross-border fire.
Warplanes also pounded 18 Hamas facilities in two waves of air strikes, according to the Israeli military.
Those raids were in response to an explosion on Saturday in which four Israeli soldiers inspecting the border fence were injured by an apparent Palestinian booby trap.
Two of the men were severely wounded but their lives were not in danger, the army said.
The blast and the retaliatory fire marked one of the most serious escalations in the Hamas-ruled territory since the group and Israel fought a war in 2014.