The armed wing of Hamas, which rules the Gaza Strip, threatened on Saturday to end a three-day-old Egyptian-brokered truce following a flurry of Israeli air strikes.

"The air raids by the Zionist enemy are new crimes. We will not stay silent in the face of the crimes," a statement from the Ezzedine al-Qassam Brigades said.

Palestinian medics said two people, including a six-year-old boy, were killed and some 24 wounded in several strikes on the coastal strip overnight and on Saturday.

A strike by an Israeli drone killed a Palestinian man, Khaled al-Burai, 25, east of Jabaliya, in the north of Gaza, a medical source said. Two other Palestinians survived the attack, witnesses said.

A medic said Ali al-Shawaf, aged six, was killed, and his father and another man wounded east of the city of Khan Yunis, but the Israeli military denied it was responsible.

"According to the findings of a preliminary investigation, what happened in Khan Yunis had nothing to do with any operation by the Israeli military," a spokeswoman said.

"The explosion that caused the death of the Palestinian child today was because of ordnance belonging to one of the terror groups," Lieutenant Colonel Avital Leibovich, the army's foreign press spokeswoman, said on Twitter.

Witnesses said Israeli aircraft carried out at least four other strikes elsewhere in Gaza on Saturday.

One targeted militants travelling in a car in the Zeitoun neighbourhood east of Gaza City after they had fired rockets into Israel, witnesses said.

Two civilian bystanders suffered minor injuries, they added.

Raids also struck the Beit Lahiya area in the north and the Nusseirat and Al-Bureij refugee camps in the centre of the Gaza Strip, without causing any casualties, witnesses said.

Overnight raids targeted two camps of the Brigades in the centre and north of the territory, and a former Hamas security post in Gaza City. They wounded about 20 people, the Hamas-run health ministry said.

Palestinian militants struck back, firing at least 39 rockets into southern Israel, most of them hitting the town of Sderot close to the Gaza border, Israeli officials told AFP, adding that one man was wounded.

The Israeli army said the latest raids were in response to rocket fire earlier in the week.

Israel held Hamas responsible for "all terrorist activity coming from the Gaza Strip," the army statement added.

In its statement, the Qassam Brigades said "nobody will be able to blame our fighters when we respond."

"If our response was not sufficient to get the message through to the enemy, we stand ready to destroy his arrogance, stop his crimes and respond to his aggression," Saturday's statement said.

On Friday, medics in the Gaza Strip reported that two Palestinians had been killed and four wounded when Israeli warplanes struck twice.

An army spokeswoman said that five of the 39 rockets fired into Israel on Saturday were intercepted by the Iron Dome air defence system, while 16 fell into the sea or fell short and landed within the Gaza Strip.

"Eighteen rockets exploded this morning in southern Israel, 16 of them in the town of Sderot," the spokeswoman said.

A police spokesman said one Israeli was wounded when a rocket hit a building in Sderot.

The violence came despite the tenuous truce between Israel and Hamas. It was announced late on Wednesday by the Brigades after a flurry of deadly exchanges in and around the territory.

The latest round of Israeli attacks and Palestinian retaliation began with air strikes Monday morning, just hours after gunmen from Sinai carried out an ambush along Israel's southern border with Egypt, killing an Israeli civilian.

Since then 14 Palestinians have been killed and dozens wounded in Israeli strikes, while at least 150 rockets and mortar shells have have hit Israel, wounding five people, among them four border police officers.

Israel has said its sudden spike in Gaza operations was "in no way related" to the Sinai border incident, with the military saying the air force was targeting militants about to attack the Jewish state.