Palestinian militants fired a barrage of rockets toward Israeli cities and villages on Saturday, drawing air strikes 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.
There were no reports of Israeli casualties as many of the rockets were intercepted and rockets alerts sent residents running to their shelters.
Gaza health officials said three Palestinians were wounded in one of the Israeli strikes.
The flare-up followed the killing in an Israeli air strike on Friday of two militants from the Islamist Hamas group which rules Gaza. The Israeli military said the air strike was a retaliation to gunfire from Gaza that had wounded two of its soldiers near the border.
Two more Palestinians were killed on Friday by Israeli forces in the often violent weekly demonstrations at the Gaza-Israel border.
Egyptian mediators, credited with brokering a ceasefire after a Hamas rocket attack north of Tel Aviv in March set off a burst of intense fighting, have been working to prevent any further escalation.
Hamas said in a statement on Thursday that its Gaza chief, Yeyha Al-Sinwar, had travelled to Cairo for talks on efforts to maintain calm along the border and alleviate hardship in the enclave.
Some two million Palestinians live in Gaza, whose economy has suffered years of blockades as well as recent foreign aid cuts. Unemployment stands at 52 percent, according to the World Bank.
Israel says its blockade is necessary to stop weapons reaching Hamas, which has fought three wars with Israel in the past decade. (Reporting by Maayan Lubell and Nidal al-Mughrabi in Gaza Editing by Gareth Jones)
