Israel has launched more air strikes on the Gaza Strip, killing at least one person and leaving more than a dozen others wounded, Palestinian medical sources said.
The escalating violence threatened to unravel Wednesday's shaky Egyptian-brokered truce which had temporarily calmed violence that erupted on Monday after a raid across Egypt's Sinai border.
Israel confirmed its aircraft had struck two Hamas security targets in Gaza overnight on Friday, calling it a response to rocket fire aimed at Israel.
Hamas medical officials said a third Israeli air raid had killed a six-year-old boy in a football field near the town of Khan Younis, and wounded two other people.
They named the dead child as Ali Alshwass.
Medical sources also said a baby was wounded in a separate attack in Rafah, at the Egyptian border.
Israel's military denied any involvement in the boy's death. A spokeswoman told Reuters news agency that "an initial examination shows the military was not involved in this incident". She had no immediate comment on the report about the baby.
She said Israel's military chiefs had scheduled urgent consultations to weigh a "course of action".
At least 10 Palestinians have been killed in missile strikes in the past week.
Earlier on Saturday, strikes targeted two camps of the armed wing of Hamas, the Ezzedine al-Qassam Brigades, in central and northern Gaza; and a former Hamas security post in Gaza City.
The attacks wounded at least 17 people, Hamas medical officials said.
On Friday, medics in the Gaza Strip reported that two Palestinians had been killed and four wounded when Israeli warplanes struck twice there.
A first Israeli air strike on Friday afternoon targeted the east of Al-Bureij in the central part of the Gaza Strip, killing Basel Ahmad, 29, who was of no known affiliation, local medical sources said.
Two other Palestinians were wounded in the strike, one of them seriously, the sources added.
Israeli aircraft "targeted a terrorist squad during preparations to fire a rocket at Israel from the central Gaza Strip. A hit was identified," the Israeli military said in a statement on Friday.
A second Israeli air strike killed another Palestinian in the north of Gaza. Hammam Abou Qadous, 20, died of his wounds after being hit as he travelled on his motorbike in the northern part of the Gaza Strip Friday evening, Palestinian medical sources said.
Two other Palestinians were slightly injured in the same attack, they added.
An Israeli army statement said "a plane of the Israeli Air Force targeted a terrorist group in northern Gaza just after the group launched a rocket that hit the Ashkelon region".
Earlier on Friday, Palestinian fighters in Gaza fired two rockets that hit southern Israel, without causing casualties or damage.
The violence came despite a tenuous Egyptian-brokered truce between Israel and Gaza's Hamas rulers that was announced on Wednesday evening by the Brigades military wing after a flurry of deadly exchanges in and around the territory.
The latest round of Israeli attacks and Palestinian retaliation began with air strikes on Monday morning, just hours after gunmen from Sinai carried out an ambush along Israel's southern border with Egypt, killing an Israeli civilian.
Israel has said that its sudden spike in Gaza operations - three deadly air raids in just over 12 hours earlier this week - was "in no way related" to the border incident, with the military saying the air force was targeting fighter about to attack the Jewish state.
Since Monday, more than 130 rockets and mortar rounds have been fired at Israel, one of which slammed into a border police post just north of Gaza, wounding four people.
The Hamas military wing said on Thursday that it had fired 120 rockets, a rare show of force from the group that had previously been observing a de facto truce.