Gaza City: Israeli war planes carried out new air strikes on Gaza overnight on Monday, wounding 35, after Israel's premier vowed no let-up against rocket-firing militants.

Hamas emergency services spokesman Adham Abu Selmiya reported at least six air strikes across the Gaza Strip, including two in Jabalia refugee camp that left 33 people injured, "mostly children."

Two strikes hit east of Gaza City, injuring two, and two more raids hit open fields, one in Beit Lahiya in the north, and a second in central Khan Yunis.

An Israeli spokeswoman confirmed the strikes saying they "targeted a weapons storage facility and four rocket launching sites in the northern Gaza Strip, as well as a rocket launching site in the southern Gaza Strip."

The renewed strikes came after Israeli Prime Minister Benjamin Netanyahu warned raids would continue "as long as necessary" and Hamas officials said efforts to broker a ceasefire through Egypt were not bearing fruit.

Violence has spiked since Friday when Israeli jets raided the Gaza Strip, killing the head of a militant group and prompting barrages of rocket fire into the Jewish state.

On Sunday, the death toll in Gaza hit 18 and Israel said more than 120 rockets had landed in its territory, wounding four.

And Netanyahu warned that operations "will continue as long as necessary."

"I have given orders to strike all those who plan on attacking us," he said during a tour of southern Israel, public radio reported.

"The Israeli army has already dealt heavy blows to the terrorist organisations," he added.

Islamic Jihad, which has claimed responsibility for most of the rocket fire into Israel since Friday, quickly issued a statement in response, vowing that "operations will continue whatever the price."

"Escalation will be met with escalation, and what is coming is even greater," the group said.

Israel's top military officer said there would be no end in sight while rocket fire continued.

"The IDF (Israel Defence Force) has been responding, and will continue to do so with strength and determination against any firing of rockets at Israel," said Chief of Staff Lieutenant General Benny Gantz.