Erez Crossing, Israel ? Israel allowed several hundred Palestinians with foreign passports to flee Gaza on Friday, even as its warplanes bombed a mosque it said was used to store weapons and destroyed homes of more than a dozen Hamas operatives.

The evacuees told of crippling shortages of water, electricity and medicine, echoing a U.N. warning of a deepening humanitarian crisis in the besieged Gaza Strip in the seven-day-old Israeli campaign. The U.N. estimates at least a quarter of the 400 Palestinians killed by Israeli airstrikes on Hamas militants were civilians.

Jawaher Hajji, a 14-year-old U.S. citizen who was allowed to cross into Israel, said her uncle was one of them — killed while trying to pick up some medicine for her cancer-stricken father. She said her father later died of his illness.

“They are supposed to destroy just the Hamas, but people in their homes are dying too,” Hajji, who has relatives in Virginia, said at the Erez border crossing between Gaza and Israel.

International calls for a cease-fire have been growing, and French President Nicolas Sarkozy is expected in the region next week.

President George W. Bush said no peace deal would be acceptable without monitoring to halt the flow of smuggled weapons to terrorist groups.

Israel has targeted Hamas leaders in the past but halted the practice during a six-month truce that expired last month. Most of Hamas’ leaders went into hiding at the start of the Israeli offensive on Dec. 27.

Israeli troops in bases in southern Israel are awaiting orders to invade Gaza.

Exiled Hamas leader Khaled Mashaal, speaking in Syria, warned that any ground assault would lead Israel to “a black destiny of dead and wounded.”

However, he said Hamas was “ready to cooperate with any effort leading to an end to the Israeli offensive against Gaza, lifting the siege and opening all crossings.”

Israel appears to be open to the intense diplomatic efforts by Arab and European leaders, saying it would consider stopping its punishing aerial assaults if international monitors were brought in to track compliance with any truce with Hamas.

Israel began its campaign to try to halt weeks of intensifying Palestinian rocket fire from Gaza. The offensive has dealt a heavy blow to Hamas but has not stopped the rockets, which continue to strike deeper and deeper into Israel. Three Israeli civilians and one soldier have been killed in the rocket attacks.

More than 30 rockets were fired into southern Israel on Friday, slightly injuring four. Sirens warning Israelis to take cover when military radar picks up an incoming rocket have helped reduce casualties in recent days.

Israeli TV showed video of a table set for the traditional Sabbath meal covered with shrapnel and broken glass.

After destroying Hamas’ security compounds early in the operation, Israel has turned its attention to the group’s leadership. Israeli warplanes on Friday hit about 20 houses believed to belong to Hamas militants and members of other armed groups, Palestinians said.