Israeli Yair Elbaz reacts after a rocket fired from the Gaza Strip hit a house he owns and rents to students in the southern Israeli town of Sderot, 18 May 2007

Israel has launched air strikes on the Gaza Strip for the second straight day, killing at least five Palestinians. And as Robert Berger reports from VOA's Jerusalem bureau, rival Palestinian factions have also been fighting each other.

Ambulances evacuated the wounded as Israeli aircraft blasted Hamas targets in Gaza. The army said it hit a Hamas headquarters and militants firing rockets. More than 100 Hamas rockets have crashed into Israel this week, terrifying residents of the border town of Sderot, which has mostly been evacuated.

Israeli spokeswoman Miri Eisen says the five-month old Gaza cease-fire is over.

"Hamas has tried to act as if they accepted the truce last November, but for the last few weeks, they have openly been accepting responsibility for terrorist acts," Eisen. said. "Hamas is a terrorist organization."

And she said, terrorist organizations must be fought.

Moderate Palestinian President Mahmoud Abbas, whose Fatah party serves in a coalition government with Hamas, called Secretary of State Condoleezza Rice and asked her to press Israel to halt the air strikes. Palestinian negotiator Saeb Erekat appealed to both sides.

"I urge all to maintain the ceasefire and I urge Israel to maintain the cease-fire," Erekat said.

The air strikes are putting further pressure on Hamas, which has been locked in fierce fighting with the rival Palestinian Fatah faction.

On Friday, clashes erupted for the sixth straight day as Fatah forces attacked the Islamic University in Gaza City, a Hamas stronghold. Frightened residents huddled indoors to escape the line of fire, while masked gunmen roamed the streets. The fighting has raised fears of a Palestinian civil war.

The dangerous mix of Israeli air strikes and Palestinians battling each other is plunging Gaza further into chaos.