Palestinian militants fired a barrage of rockets toward Israeli cities and villages on Saturday, drawing airstrikes from Israeli aircraft, the Israeli military said.
Israel Radio said at least 50 rockets were fired in the space of about 30 minutes, some deep into southern Israel.
Rockets could be seen flying through the sky over the coastal city of Ashkelon, located about 12 kilometres from the Gaza Strip.
There were no reports of Israeli casualties as many of the rockets were intercepted and sirens sent residents running to their shelters.
Gaza health officials said three Palestinians were wounded in one of the Israeli strikes.
A pillar of thick smoke was visible over Gaza City on Saturday morning. The flare-up followed the killing in an Israeli airstrike on Friday of two militants from the Hamas group that rules Gaza.
The Israeli military said the airstrike was a retaliation to gunfire from Gaza that had wounded two of its soldiers near the border on Friday.