The Israeli military has launched several air strike on positions controlled by Gaza's rulers Hamas in response to a rocket fired across its border late on Sunday.
Israel's Iron Dome system intercepted the missile that was fired from the enclave, the Israeli military said.
Hamas has not claimed responsibility for the rocket fire but Israel holds it responsible for any fire that emanates from the enclave.
The latest raids follow strikes by the Israeli army on two Hamas posts on Sunday, after balloons carried an explosive device over the border fence.
The Gaza border has been relatively calm in recent weeks after a deal in which Israel allowed Qatar to provide millions of dollars worth of cash for fuel and salaries in the blockaded enclave.
Following Sunday's strikes, the Israeli army statement said: "Earlier today, an explosive device attached to multiple balloons was launched on a model airplane from the Gaza Strip into Israeli territory.
"In response, (Israeli) attack helicopters targeted two Hamas military posts in the Gaza Strip."
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A Hamas security official said one strike occurred east of Khan Younis in the southern Gaza Strip and hit an observation point for Hamas's armed wing, while the second was east of Gaza City.
The security official said no injuries had been reported.
Israel and Palestinian militants in Gaza have fought three wars since 2008.
Since March, protests and clashes have occurred along the Gaza border fence.
Protesters have been calling for Palestinian refugees to be allowed to return to their former homes now inside Israel. Israelis say that would mean the destruction of the Jewish state.
At least 240 Palestinians have been killed since the demonstrations began, most of them by Israeli fire during border clashes but also by air and tank strikes.
Two Israeli soldiers have been killed over the same period, one by a Palestinian sniper and another during an aborted special forces operation inside Gaza.