Israeli warplanes struck Gaza on Friday in retaliation for incendiary balloons launched from the Palestinian enclave, the latest outbreak of hostilities since a ceasefire ended 11 days of conflict in May.
Security sources with Hamas, the militant group that runs the blockaded territory, said the strikes hit training sites. There were no injuries reported.
The Israeli army said its fighter jets struck "a weapons manufacturing site belonging to the Hamas terror organisation" in response to "arson balloons fired towards Israeli territory".
Incendiary balloons caused four minor fires in the Eshkol region bordering Gaza on Thursday, Israel's fire service said.
The fires were "small and not dangerous" and were quickly brought under control, it said.
There was no immediate indication as to which Gaza-based group was responsible for the balloon launches.
Eleven days of deadly fighting between Israel and Hamas, as well as other Palestinian armed groups based in the enclave, ended on May 21 with a ceasefire declaration.
There have been several flare-ups since the ceasefire, including Israeli air strikes after incendiary balloon launches last month.
After an exchange of fire on June 18, Israel's army chief ordered forces to be ready "for a variety of scenarios, including a resumption of hostilities".
The conflict killed 260 Palestinians including some fighters, according to Gaza authorities.
In Israel, 13 people were killed, including a soldier, by rockets fired from Gaza, the police and army said.
Israel and Egypt have maintained a blockade on Gaza since 2007, the year Hamas took power. Israel says the measure is necessary to contain armed groups in the enclave.