Israel launched airstrikes against targets of the radical group Hamas in the Gaza Strip in the early hours of Wednesday (local time), after its territory was attacked with incendiary balloons from that side of the border, the Israeli Armed Forces confirmed.
So far no deaths or injuries have been reported in Israel or Gaza,
but the mutual attacks are the first violent act since the truce reached on May 21, which ended 11 days of fighting between the two sides.
Those clashes left 256 Palestinians dead, including 66 children, according to the Gaza authorities.
At least 12 people in Israel also lost their lives.
Palestinians in Gaza launched the incendiary balloons that set at least 20 fires in southern Israel in response to a march by hundreds of Israeli ultranationalists through East Jerusalem, in which protesters celebrated the capture of that disputed city in 1967 by Israel.
Palestinians viewed the parade - in which some Israelis shouted hateful phrases such as "Death to the Arabs" and "Let your village burn" - as a provocation and a show of force.
Hamas, the group that controls Gaza, called on people there to "resist" the march.
The Israeli Armed Forces said in a statement that its fighter jets had reached Hamas-operated military complexes in Khan Yunis and Gaza City.
The statement added that "terrorist activity" had taken place in those military compounds and
that Israel was "prepared for all scenarios, including the resumption of hostilities
, in the face of continued terrorist acts in the Gaza Strip."