Updated

A 12-hour humanitarian cease-fire has begun to allow civilians in Gaza to receive aid and evacuate to safer areas.

The Israeli military says Saturday's 12-hour pause began at 8 a.m. (1:00 a.m. EST, 0500 GMT). It warned the military "shall respond if terrorists choose to exploit" the lull to attack Israeli troops or civilians. The military said "operational activities to locate and neutralize tunnels in the Gaza Strip will continue."

Previous humanitarian cease-fires have been cut short by fighting.

Civilians on both sides have been hardest hit over the past 18 days. Nearly 900 Palestinians and 40 Israelis have been killed.

The lull was agreed upon by both sides after U.S. Secretary of State John Kerry failed to broker a weeklong truce as a first step toward a broader deal.