The IDF called up 16,000 reserves on Wednesday night, and the soldiers have been deployed to positions on Thursday. A total of 86,000 reservists have been called up since the start of the war.
Several clashes occurred between the IDF and Hamas overnight between Wednesday and Thursday. The Givati Brigade's Tzabar Battalion killed two terrorists in gun battles in southern Gaza early in the morning.
A Golani infantry brigade unit saw a terrorist surfacing from a tunnel on Thurday morning, killing the gunman.
Paratroopers identified five terrorists and dispatched an air force craft, which struck the suspects, killing them.
The IDF is examining a number of shafts found in Gaza to see if they are connected to new tunnels, or to underground passages that the army already knows about.
The IDF destroyed several tunnels in the past 24 hours, a senior IDF source said Thursday morning.
The air force is continuing to strike Hamas and Islamic Jihad targets, based on newly arrived intelligence, some of which comes from ground forces inside Gaza. It destroyed 110 targets in the past 24 hours, the army source said, and 4,200 targets since the start of hostilities.
On Wednesday, Defense Minister Moshe Ya'alon spoke by phone with his American counterpart Chuck Hagel, who called for a humanitarian cease-fire in Gaza that would lead to a permanent end in fighting along with the disarmament of Hamas.
Hagel's call came amid US concern over the rising number of deaths on both sides of the conflict, said Pentagon spokesman John Kirby.
The US secretary of defense stressed that any comprehensive resolution to the over three-week conflagration would need to result in the demilitarization of Hamas and other terrorist groups in Gaza.
Hagel also reiterated Washington's stance in support of Israel's right to defend itself from attempts to harm its citizens. Ya'alon in turn thanked Hagel for his expression of support for Israeli defense, citing especially US contributions for the development of the Iron Dome rocket defense system.
Separately, the Pentagon said it had allowed Israel to stock up on grenades and mortar rounds from a US munitions store located in Israel as part of bilateral emergency preparedness arrangement.
The security cabinet on Wednesday approved continuing Israel's campaign launched on July 8 in response to a surge of rocket attacks by Gaza's dominant Hamas Islamists. But Israel also sent a delegation to Egypt, which has been trying, with Washington's blessing, to broker a ceasefire.
Israel briefly halted its strikes in Gaza after accepting an Egyptian truce proposal on July 15, but resumed attacks the next day as terrorists in Gaza pounded Israel with fresh salvos of rockets.
Reuters contributed to this report.