Updated

The Palestinian civilian death toll mounts as Israel ferociously pursues Gaza Strip militants who are menacing nearly half of Israel's population with rocket fire.

Early on Monday, an airstrike leveled two houses belonging to a single family, killing two children and two adults and injuring 42 people, said Gaza heath official Ashraf al-Kidra. Rescue workers were frantically searching for 12 to 15 people under the rubble.

Shortly after, Israeli aircraft bombarded the ruins of the former national security compound in Gaza City. Al-Kidra says flying shrapnel killed one child and wounded others living nearby.

The rising toll was likely to intensify pressure on Israel to end the fighting. Hundreds of civilian casualties in an Israeli offensive in Gaza four years ago led to fierce international condemnation of Israel.