Israel launched air strikes on the Gaza Strip, in retaliation for incendiary balloons fired from the territory.
Loud explosions were heard in Gaza City in the early hours of Wednesday.
Several balloons were sent from Gaza into Israel earlier on Tuesday causing multiple fires, Israeli fire service said.
It is the first major flare-up since 11 days of fighting between the two sides ended in a ceasefire on 21 May.
It followed a march by Jewish nationalists in occupied East Jerusalem on Tuesday, which had drawn threats from Hama, the group that runs Gaza.
It is unclear if the attacks caused any deaths or injuries.
This is the first violent exchange since Israeli’s new coalition government came to power last weekend, headed by Naftali Bennett and drawing an end to Benjamin Netanyahu’s 12-year run as prime minister.
In a statement, the Israel Defense Forces (IDF) said its fighter jets had hit military compounds operated by Hamas in Khan Yunis and Gaza City.
It said “terrorist activity” took place in the compound, and that the IDF was “prepared for all scenarios, including the resumption of hostilities, in the face of continued terror acts from the Gaza Strip”.