Israel may step up military operations to suppress incessant rocket attacks from the Gaza Strip, said Israeli Defense Minister Ehud Barak Monday during his visit to a joint Israel-U.S. air-defense maneuver.

"All in all, these are very important days, for both advancing our cooperation in missile defenses in the face of future challenges and continuous action against Hamas and militant organizations in Gaza, which may intensify and broaden," a statement released by Barak's office quoted him as saying.

Barak made the remarks while viewing a live interception of airborne targets by a Patriot anti-aircraft missile battery deployed in an undisclosed location in central Israel as part of a bilateral air-defense drill code-named Austere Challenge 12.

Some 3,500 Israeli and U.S. troops are participating in the three week-long exercise, the largest of its kind to date, which simulates responses to simultaneous mass missile attacks on Israel from several fronts.

Meanwhile, in and around Gaza, air defenses were anything but simulated, as Palestinian militants in the coastal enclave lobbed more rockets at southern Israel on Monday amid failed Egyptian efforts to mediate a cease-fire agreement.

Some 10 rockets were fired into Israel by mid-day, bringing the total number of projectiles fired at Israeli cities and communities to more than 100 since cross-border hostilities flared up on Saturday.

Israeli Air Force craft launched retaliatory airstrikes overnight Sunday, targeting a smuggling tunnel, a weapons storage and rocket-launching sites in the northern and southern Gaza, after three Israeli civilians were wounded earlier in the day, the military said.

Airstrikes have so far killed five Palestinians and wounded scores of others in Gaza, according to Palestinian sources.

Israel's leaders responded Monday to the escalation along the border, warning Hamas and other militant groups of "severe repercussions" for the ongoing rocket fire.

On Sunday, Prime Minister Benjamin Netanyahu, who is reportedly working with other top officials to muster international legitimacy for a wide-scale foray into Gaza, said Israel is prepared to "intensify" its military operations.