A possible Israeli ground operation in the Palestinian territory, however complex in the wake of the army's historic withdrawal from the Gaza Strip on 12 September, is being discussed by Israeli defence officials, Israeli radio said.
After convening an emergency meeting of his top officials in Tel Aviv to evaluate the situation, Israeli Defence Minister Shaul Mofaz ordered a tough response to rocket fire from Gaza, Israel radio reported.
Israel said its forces would concentrate on the northern end of Gaza, allegedly from where most rockets were launched at Israeli border towns, Israel radio reported. It would also target Hamas from the air.
Israel launched missile attacks after five Israelis were wounded when al-Qassam Brigades, the military wing of Hamas, fired a number of rockets at the Israeli town of Sderot in retaliation for what it said was an Israeli attack on Jabalya.
Al-Nasir Salah al-Din Brigades of the Popular Resistance Committees had also fired three rockets at Sderot in retaliation for attacks on Jabalya.
"The missile attack is yet another evidence to Israeli total disregard for Palestinian blood... It is also an indication that although Israel has been defeated on the ground in Gaza, it still has control over the air and sea"
Hamas representative in Beirut
A total of 30 homemade rockets were launched from Gaza into Israel since Friday afternoon.
Tel Aviv said it responded by firing missiles at several suspected Hamas weapons workshops in the Gaza and sealed off both the West Bank and the Gaza Strip.
The overnight rocket barrage was the first since Israel pulled out of Gaza nearly two weeks ago.
Israel had earlier said it would display "zero tolerance" for attacks on its towns after its pullout from the area.
Hamas holds Israel responsible for what it says was an attack on the resistance movement's military parade in Jabalya on Friday that killed 19 Palestinians and wounded more than 80.
But the Israeli army has denied any involvement in Jabalya's deadly explosion.
Meanwhile, Aljazeera correspondent in Gaza, Wail Dahduh, reported multiple sonic booms by Israeli military aircraft over Gaza.
Hamas blames Israel for Friday's
blast which killed 19 people
The Palestinian Interior Ministry confirmed the report.
Earlier on Saturday, several Israeli helicopters bombed homes belonging to members of Hamas, in Jabalya north of Gaza and al-Zaitun neighbourhood south of Gaza.
Aljazeera's correspondent said the aerial bombing wounded three Palestinians and caused extensive damage to at least three homes.
Hamas said at a press conference that physicians had found fragments of an electronic panel - allegedly from electronic systems in Israeli missiles - in the "body of one of our martyrs", which Hamas spokesman Sami Abu Zuhra said confirmed Israel's involvement in Friday's Jabalya attack.
Hamas vowed retaliation and denounced the Palestinian Authority's (PA) explanation for it.
"The Palestinian Authority security organs have received what has confirmed that the explosion was an internal incident. All parties should shoulder their responsibilities in such occasions instead of hiding behind the pretext of the [Israeli] occupation"
Tawfiq Abu Khusa,
PA Interior Ministry spokesman
Speaking to Aljazeera on Friday, Hamas representative in Beirut Usama Hamdan said witnesses had reported seeing Israeli missiles being fired at them, and expressed dismay over PA statements made minutes after the attack which said the matter was an "internal incident".
"The missile attack is yet another evidence to Israeli total disregard for Palestinian blood in the absence of an official stance defending it.
"It is also an indication that although Israel has been defeated on the ground in Gaza, it still has control over the air and sea," Hamdan said.
Israel denied any involvement in the explosion.
Another Aljazeera correspondent in Gaza, Hiba Akila, said there had been a number of conflicting reports about the Jabalya explosion.
Hamas spokesman Sami Abu Zahra said: "The Israeli occupation bears full responsibility for the crime that occurred in Jabalya.
"Several people, including myself, testify that we had seen Israeli drones that fired the missiles at al-Qassam brigades."
Witnesses say they saw Israeli
military drones firing missiles
But PA Interior Ministry spokesman Tawfiq Abu Khusa said: "The Palestinian Authority security organs have received what has confirmed that the explosion was an internal incident. All parties should shoulder their responsibilities in such occasions instead of hiding behind the pretext of the [Israeli] occupation." Another Hamas spokesman explained that the rockets and Qassam missiles exhibited during the resistance movement's military parade on Friday were clearly "plastic models" as could be seen by anyone close enough or by zooming a camera in on any of the models.
Aljazeera also interviewed the spokesman for the Israeli army, Itan Arousi.
"The Israeli army is set to administer the appropriate response, whether military or diplomatic to any actions, but we cannot give details of our programme.
Our military operations will be exclusively directed against Hamas members and their locations," he said.
"Hamas is responsible for the dangerous explosion in Jabalya and it was Hamas which threaten Gaza residents. But when they (Hamas) fail or make mistakes, they accuse Israel without any evidence"
Israeli army spokesman
"The question in my view should be why terrorist organisations stage terror operations against Israel after we have evacuated Palestinian areas. We pulled out without any problems two weeks ago.
"Hamas is responsible for the dangerous explosion in Jabalya and it was Hamas which threaten Gaza residents.
"But when they (Hamas) fail or make mistakes, they accuse Israel without any evidence.
"We are running a democratic state while the army complies to the orders given by the Israeli government," he added.