The IDF has begun warning residents of northern Gaza and other areas in the Strip from which heavy and long-range rockets are being fired at Israel, to leave ahead of a stepped-up campaign of air raids that will target Hamas leaders hiding under large residential buildings, a senior army source said on Saturday night.“We are moving to a more significant [stage]. Since the leaders are hiding under homes and using human shields, we are initiating the evacuation of civilians in Gaza before stepping up attacks. Until now, we’ve tried to use minimal force to lower civilian casualties.That explains how, even though we have hit 1,300 targets, the civilian casualty rate is so low,” the source said.“But in order to improve effectiveness in our operations in northern Gaza and other areas, we will in the coming hours evacuate civilians for their own safety from places where rocket fire has occurred,” he added.Residents of the Gaza Strip in areas that the IDF will soon strike will receive information, via phone or other media, informing them that terrorist elements are operating in their area and that they must leave for their own safety.“I am confident most will leave,” the army source said.“Then, there will be much more significant attacks.”Some Hamas leaders are hiding under Gaza hospitals, he said.The source described rocket barrages on Tel Aviv on Saturday night as a form of “psychological warfare,” adding that Hamas has been pushed into a corner and was now seeking to step up its threats.The IDF is fully ready to carry out a ground offensive if ordered to do so, he said.“There is a large order of battle [force] ready for the command.A ground maneuver is one way to obtain achievements.The option is on the table, and can be activated within a short time. It’s a matter of making a decision,” the source said.Hamas and Islamic Jihad tried to emulate Hezbollah and even improve on the Lebanese terrorist organization’s tactics of firing on the Israeli home front, the source added. “They want to kill civilians and spread fear. “We’ve dealt with bigger challenges, like the suicide bus bombings that left many victims dead [in the last decade],” he said.“Hamas and Islamic Jihad failed in their attacks, which they have planned and prepared up for years. They planned to kill as many civilians as they could with rockets and tunnel and underwater attacks. All of these have failed,” he added.He praised Israel’s aerial, land, and naval defenses, saying that “the air defense is very impressive. It has reached a very high level of effectiveness, approaching 100 percent, though it’s not total.”The more time that goes by, the more damage Hamas and Islamic Jihad will sustain, he said.