JERUSALEM – Israeli aircraft pummeled the rocket arsenals of Gaza militants early today and signaled a ground invasion might be growing near as troops, tanks and armored personnel carriers massed near Israel’s southern border with the Palestinian territory.

Fighting between the two sides escalated sharply Thursday with a first-ever militant attack on the Tel Aviv area, menacing Israel’s heartland. No casualties were reported, but three people died in the country’s rocket-scarred south when a projectile slammed into an apartment building.

The death toll in the densely populated Palestinian territory climbed to 19, including five children according to Palestinian health officials, as waves of Israeli fighter planes and drones sent missiles hurtling down on suspected weapons stores and rocket-launching sites.