The IDF has struck 2,600 Hamas and Islamic Jihad targets since the start of Operation Protective Edge, and some 500 targets since the start of the ground offensive. Air strikes are expected to intensify in northern Gaza, where a concentration of rocket launchers is located, a senior military source said. The IDF has uncovered 36 tunnel shafts and 14 tunnels, some of which are underground cross-border attack structures.Inside the tunnels, soldiers have found RPGs, bombs, sedatives, booby traps, and communication devices. Some of the tunnels featured mini bunkers, the source added. "We are blowing them up. A large tunnel was found and destroyed. We'll destroy more in the future," he said. IDF control centers that manage sensor to shooter cycles have overseen strikes on several rocket launching squads in Gaza that were about to fire at Israel, the source added. Terrorists on the ground are increasing gun and missile attacks on IDF units on the ground, the source said. The ground units "are not static. They are dynamic and moving, to search for additional targets and engagement in the areas they took," he said.Large numbers of Ground Forces entered the Gaza Strip overnight between Saturday and Sunday as Israel expanded its operation against Hamas. The increased presence in Gaza is aimed at destroying Hamas infrastructure, the IDF said. On Sunday, Col. Rasan Alian, commander of the Golani Brigade, was moderately injured in an exchange of fire in Gaza. He has been hospitalized at the Soroka Medical Center in Beersheba.At least 20 Palestinians were killed in a Gaza neighborhood on Sunday, a health officials said.