Moawiya Hassanein, head of the Palestinian emergency services in Gaza, said three Palestinian children - aged two, four and 11 - were hit by flying glass in the raid.
Helicopters struck twice in the central refugee camp of Nusseirat, destroying a metal foundry, but no one was injured.
An Israeli military spokesman confirmed the attacks, saying they had targeted two weapons-manufacturing plants and two arms caches. There was no independent confirmation of the Israeli claim.
Ismail Haniya, the Hamas leader in Gaza, blamed Israel for the increase in tensions.
"We in the Palestinian government condemn this escalation and call on our Arab brothers in particular and the international community in general to intervene in order to stop targeting our people and the escalation against them everywhere, particularly in the Gaza Strip," he said.
Fawzi Barhoum, a Hamas spokesman, told Al Jazeera that Hamas held the Israeli government led by Binyamin Netanyahu responsible for the "escalation" and said the air raids had been expected because of threats by Ehud Barak, the defence minister, and other ministers.
He also blamed "the international community and the Arabs" for failing "to do anything about the situation in Gaza".
"The absence of the international community and the Arabs has allowed the Israelis to escalate the situation," he said.
|A Palestinian man inspects the damage at a cheese factory hit by Israel [AFP]
But Silvan Shalom, Israel's deputy prime minister, adopted a defiant stand and warned of more attacks on Gaza.
"If this rocket fire against Israel does not stop, it seems we will have to raise the level of our activity and step up our actions against Hamas," Shalom told public radio on Friday.
"We won't allow frightened children to again be raised in bomb shelters and so, in the end, it will force us to launch another military operation," he said.
Israel's air attacks came after a rocket fired from Gaza landed near the southern Israeli city of Ashkelon late on Thursday, causing damage but no casualties, the army said.
Hamas leaders say they have contacted armed groups in the coastal territory accused of firing rockets in an apparent bid to calm tensions with Israel.
Israel holds Hamas responsible for maintaining security in Gaza and halting the rocket attacks.
Call for restraint
Britain on Friday expressed concern at the escalation in and around Gaza, calling for restraint and the launch of US-backed indirect talks between Israel and the Palestinian Authority.
"We are concerned by today's strikes and the escalation of violence in Gaza and southern Israel over the past week. We call on all parties to show restraint," a foreign office spokeswoman said on Friday.
"We encourage Israelis and Palestinians to focus efforts on negotiation and to engage urgently in US-backed proximity talks."
Palestinian news agencies reported that Israeli aircraft dropped leaflets over parts of Gaza on Thursday warning residents of retaliation for last Friday's killing of soldiers in Khan Younis.
Two Israeli soldiers, including an officer, were killed along with two armed Palestinian men during fierce clashes when Israeli tanks made a brief incursion into Gaza.
On Tuesday, a Palestinian teenager was killed as Israeli troops fired on protesters near the border of the blockaded coastal strip.