The Israeli army said it fired at unspecified Hamas "military targets" in Gaza on Wednesday after a Palestinian bomb attack on an army engineering unit working inside the Hamas-ruled territory.
No Israelis were reported injured in the explosion, which the army's radio station said appeared to have targeted a mechanical digger.
The army said the bomb was planted under cover of mass protests along the Gaza-Israel border since March 30.
"During routine activity in northern Gaza, an explosive device that was placed under the guise of the riots was detonated against an (army) engineering vehicle on the western side of the security fence," a military statement said.
"In response, the Israel Defence Forces struck a number of Hamas military targets," it added.
The statement did not give the location of the targets or the type of military fire used. Israel has used both tank fire and air strikes against Hamas targets in the past.
It was also not clear what the engineering unit was working on, though Israel routinely carries out maintenance work on the border fence.
The mass rallies, under the name "the Great March of Return," call for Palestinian refugees to be allowed back to their former homes now inside Israel.
They have led to clashes in which Israeli forces have killed 31 Palestinians. No Israelis have been hurt.