The Gaza border has been relatively calm in recent weeks after a deal in which Israel allowed Qatar to provide millions of dollars in aid for fuel and salaries in the blockaded enclave.
"Earlier today, an explosive device attached to multiple balloons was launched on a model airplane from the Gaza Strip into Israeli territory," an Israeli army statement said.
"In response, (Israeli) attack helicopters targeted two Hamas military posts in the Gaza Strip."
A Hamas security source said one strike occurred east of Khan Yunis in the southern Gaza Strip and hit an observation point for Hamas's armed wing, while the second was east of Gaza City.
Hamas arrests Gaza men suspected of attacking Abbas's TV station
The security source said no injuries had been reported.
Israel and Palestinian in Gaza, run by movement Hamas, 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.
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.
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