The IDF is ready for a large operation in Gaza, Defense Minister Ehud Barak said on Saturday, but warned against rushing into any such offensive. Speaking a day after Hamas's most intense wave of shelling of the South since the cease-fire began in June, Barak cited the Second Lebanon War with Hizbullah in 2006 to illustrate the harmful consequences of a knee-jerk response. "The time may come when there will be a need for a broad operation, because we cannot accept the ongoing violation of the truce. But getting carried away is not a policy," he said during an address to a legal forum at the Netanya Academic College. Barak said he was "the minister of defense, not the minister of war," adding, "Believe me, I knew war, I know what a battle is, and I am not deterred by these when they are needed." The military was ready for a large operation, he said. "If the need will arise, the IDF and the security forces are ready for a powerful operation that will be painful for the other side. But security is not a matter of pride. Two years ago, we saw what an overly-rushed decision can do to Israeli security." A Gaza operation "would not be a picnic," he said, adding that one should be launched only after "all other options have been tried." The cease-fire is due to expire on December 19. Barak defended his decision in June to opt for a six-month Gaza truce, saying it had allowed "school children in Sderot to walk to school under a sky clear from Kassam rockets." And while Hamas was exploiting the "security calm" to arm itself and to build up its war infrastructure, Israel could "deal with that too," he said. He hinted that Israel could cut off the supply of electricity from its grids to Gaza in the future, and scale back its responsibility for border crossings with the Strip. Barak added that he was seeking government and judicial approval for the IDF to act against residential areas in Gaza from which terrorists fired rockets at Israel. A warning about impending IDF action would be transmitted before striking, Barak said, sketching out a potential new policy. The defense minister insisted that the truce had not damaged attempts to secure the release of kidnapped tank gunner St.-Sgt. Gilad Schalit. Earlier on Saturday, Hamas threatened to resume its heavy bombardment of the South, hours after two gunmen from the Popular Resistance Committees were killed in an explosion in northern Gaza. The army denied any connection with the blast and rejected Palestinian claims that the air force had struck the two gunmen. The men died when their own explosives were accidentally set off in a "work accident," the IDF said. On Friday, Sderot and Ashkelon were struck by heavy rocket fire. An elderly woman was lightly wounded by shrapnel and two people went into shock in Sderot, while 15 were treated for shock in Ashkelon. They were all evacuated to Ashkelon's Barzilai Medical Center. Ashkelon was targeted by five rockets on Friday morning, identified by security officials as Grad-type rockets, which have a longer range and carry more explosives than Kassams. Air raid sirens rang out across Ashkelon throughout Friday, sending residents ducking for cover as the city was rocked by a series of powerful explosions. Children on their lunch break were caught in the rocket fire and rushed back into their schools in panic. Three rockets hit in the city and two struck open areas. Hamas's Izzadin Kassam Brigades said it was behind the attacks. Large numbers of police and rescue officials flooded areas where the rockets fell. Earlier on Friday morning, Sderot was hit by 10 rockets. The IDF Home Front Command instructed residents to remain in protected rooms throughout the day on Friday. Prime Minister Ehud Olmert convened a meeting with security chiefs at the Defense Ministry in Tel Aviv on Friday afternoon. Israel would not accept the targeting of its southern communities, he said, describing the rocket fire as "a fundamental and callous violation of the understanding that led to the cease-fire." Israel had "no intention of accepting these events," he said. Gaza-periphery communities would not return to the state of uncertainty that they faced several months ago, before the cease-fire went into effect, Olmert vowed. Israel would continue to pressure the Hamas regime by keeping border crossings with Gaza sealed and employing a number of other measures, the prime minister said. Defense sources suggested that Hamas had initiated Friday's bombardment as part of a bid to force Israel to accept a revamp of the cease-fire. Hamas is reportedly seeking to change the conditions underpinning the faltering, soon-to-expire truce, which allows Israel to enter Gaza and close off border crossings at will. Following the bombardment, Barak, accompanied by Deputy Defense Minister Matan Vilna'i and OC Southern Command Maj.-Gen. Yoav Galant, toured Sderot and inspected rocket impact sites. Barak met with incoming Sderot Mayor David Buskila and local Home Front Command, police and rescue services officials. The defense minister linked the shelling of southern Israel with the killing of 12 Hamas gunmen by the IDF in two recent IDF incursions into the Strip, raids that were aimed at preventing attacks on troops. He vowed to "continue defending IDF soldiers and civilians with force, and to thwart attempted terrorist attacks when we identify them. "Together with that, if the other side wishes to continue with the cease-fire, we will certainly weigh that in a positive light. [But] we cannot accept this intermediate stage, with its barrages of rockets." In Sderot, Barak shied away from directly answering a question on whether the truce had ended, saying he did not want to get carried away. "Serious decision-making" was the main goal, Barak said. "At the same time, we have a duty to protect the residents... We cannot accept this kind of fire," he warned.