Israel is threatening to invade the Hamas-ruled Gaza Strip in response to escalating Palestinian rocket attacks. Israel has already stepped up air strikes, killing 31 Palestinians, about half of them civilians, since Wednesday. An Israeli civilian was also killed Wednesday in a rocket attack. Robert Berger reports from the VOA bureau in Jerusalem.

Deputy Defense Minister Matan Vilnai says Israel has no other choice but to launch a major military offensive in Gaza.

Vilnai told Army Radio that the more rocket fire intensifies and reaches a longer range, the bigger the "holocaust" that the Palestinians will bring upon themselves. The use of the term "holocaust" outside of the Nazi genocide of World War II is rare in Israel, and appeared to underscore the gravity of the situation. Vilnai said Israel is prepared to use all its military might to defend itself.

The sharpening rhetoric follows Palestinian rocket attacks on Thursday on the major Israel city of Ashkelon, north of the Gaza Strip. Several Iranian-made Grad rockets slammed into the city, hitting an apartment and near a school. It was the deepest rocket strike ever on Ashkelon, and effectively redraws the frontline of the conflict. Until now, the coastal city was largely out of missile range, and most rocket fire was directed at the small town of Sderot near the Gaza border.

The Islamic militant group Hamas, which rules Gaza, says it targeted Ashkelon in response to escalating Israeli air strikes which are taking a heavy toll on both fighters and civilians.

"So I think Israel tries to make Gaza sink in the ocean of blood and tears and suffering," said Hamas official Ghazi Hamad. "And maybe it tried to impose some collective punishment against [the] Palestinian people."

The Gaza crisis will be high on the agenda when U.S. Secretary of State Condoleezza Rice visits here next week. Rice has urged Israel not to invade Gaza, but Israeli officials will tell her they are running out patience.