Israeli aircraft hit five Hamas targets in Gaza in retaliation to mortar rounds fired at Israel from the coastal territory run by the Islamic militant group.
The military did not specify what was hit on Wednesday, saying only that "Hamas terrorist infrastructure" was targeted in southern Gaza.
Palestinian media reported that open areas were struck as well as a guard post.
No injuries were reported.
Israel earlier said it responded with tank fire to a mortar shell launched toward Israeli forces near the southern Gaza Strip.
The army said no soldiers were harmed.
Israel blamed Hamas for launching the mortars and a military spokesman, Lieutenant Colonel Peter Lerner, called the violence "the most serious" escalation since the 2014 war.
Last month, Israel discovered and destroyed a tunnel dug from Gaza into Israel - the first to be found since the 2014 Gaza war.
That discovery sparked concerns in Israel that Hamas was rebuilding its underground tunnel network in preparation for the next conflagration.
In 2014, Israel destroyed more than 30 tunnels Hamas had dug under the border.
More than 2200 Palestinians, about two-thirds of them civilians, were killed in the 50-day summer war.
On the Israeli side, 66 soldiers and seven civilians were killed.
Israel and Hamas have largely observed a ceasefire since the war, but other militant groups also operate in Gaza.
There was no immediate claim of responsibility for the mortar fire, and Israel says it holds Hamas responsible for any attacks out of the territory.
While it stopped short of claiming responsibility for the mortar fire, Hamas' armed wing said in a statement Wednesday that Israeli forces had made "incursions" into Gaza and that it would "not allow for this aggression to continue".
The escalation comes amid a wave of violence that has seen almost daily attacks by Palestinians, mostly stabbings, which have killed 28 Israelis and two Americans.
Some 193 Palestinians have been killed, most said by Israel to have been attackers and the rest killed in clashes with Israeli forces.
