Exiled Hamas leader Khaled Meshaal said from Damascus Friday that his militant group was prepared for an Israeli ground invasion of the Gaza Strip and could abduct abduct more soldiers if Israel attempts the incursion.

"If you commit a foolish act by raiding Gaza, who knows, we may have a second or a third or a fourth Shalit," he said, according to Reuters. Israeli soldier Gilad Shalit was kidnapped by Hamas in a cross-border raid more than two years ago.

Israel bombed a mosque it claimed was used to store weapons and destroyed homes of more than a dozen Hamas operatives Friday, but under international pressure, the government allowed hundreds of Palestinians with foreign passports to leave besieged Gaza.

In last 48 hours, the U.S. government has helped 27 Americans get out of Gaza, and has heard no reports of any Americans being injured during the week-long assault, according to State Department spokesman Gordon Duguid. Evacuated Americans were taken by bus to Amman, Jordan, but more Americans are believed to be in Gaza.

Israel has been ringing with artillery, armor and infantry in an indication the week-old air assault against Gaza's Hamas rulers could soon expand with a ground incursion. Senior leadership in Israel gave a thumbs up to ground invasion, making it appear that such an attack could happen very soon, FOX News has learned.

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Israel showed no sign of slowing its blistering seven-day offensive against Hamas militants in Gaza as Hamas ordered a "day of wrath" against Israel over the killing of a senior commander.

Thousands of Israeli security personnel were placed on high alert and deployed around annexed Arab East Jerusalem after Hamas called for "massive marches" following the main weekly Muslim prayers.

"Police has been placed on a heightened state of alert throughout the country, just under the maximum level that is in effect in war time," a police spokesman told AFP.

In another strike Friday the Israeli Air Force bombed the house of top Hamas operative Imad Akel. The Israeli military reported hearing secondary blasts at the house, indicating the presence of a stash of weapons and explosives in the home, the Jerusalem Post reported.

Israel launched the aerial campaign last Saturday in a bid to halt weeks of intensifying Palestinian rocket fire from Gaza. The offensive has dealt a heavy blow to Hamas, but failed to halt the rocket fire. New attacks Friday struck apartment buildings in the southern Israeli city of Ashkelon, though no serious injuries were reported.

The United Nations estimated Friday that around 100 civilians have been killed in Gaza in the past week, around 25 percent of the 400 estimated killed in the bombing campaign.

The Israeli military called at least some of the houses ahead of time to warn inhabitants of an impending attack. In some cases, it also fired a sound bomb to warn away civilians before flattening the homes with powerful missiles, Palestinians and Israeli defense officials said.

Israel opened its border with Gaza Friday to allow 270 Palestinians with foreign passports to flee, mostly Russian and Georgian women who are married to Gazans. Those who remained behind faced stark conditions in Gaza, which has lost electricity and running water in most areas.

"There is no water, no electricity, no medicine. It's hard to survive. Gaza is destroyed," said Jawaher Haggi, a 14-year-old Palestinian American. She said her uncle was killed in an airstrike when he tried to pick up some medicine for her cancer-stricken father, who died of his illness several days later.

Secretary of State Condoleezza Rice said Friday that the U.S. government continued to seek a "durable and sustainable" cease-fire between Israel and Hamas, but blasted the militant group, which she said has "held the people of Gaza hostage" since taking power in a 2007 coup.

Rice said she was in "constant contact with key Arab states" as she tried to mediate the conflict, but said she had no plans to travel to the Middle East to broker any deal.

The White House, in a separate statement, said that Hamas must stop all of its rocket attacks on Israel, which has a right to defend itself, Reuters reported.

After destroying Hamas' security compounds, Israel turned its attention to the group's leadership.

In airstrike after airstrike early Friday, Israeli warplanes hit some 20 houses believed to belong to Hamas militants and members of other armed groups, Palestinians said.

They said the Israelis either warned nearby residents by phone or fired a warning missile to reduce civilian casualties. Israeli planes also dropped leaflets east of Gaza giving a confidential phone number and e-mail address for people to report locations of rocket squads. Residents stepped over the leaflets.

Israel used similar tactics during its 2006 war in Lebanon.

Most of the targeted homes Friday belonged to activist leaders and appeared to be empty at the time, but one man was killed in a strike that flattened a building in the Jebaliya refugee camp in northern Gaza.

More than 400 Gazans have been killed and some 1,700 have been wounded in the Israeli campaign, Gaza health officials say. The number of combatants and civilians killed is unclear, but Hamas says around half of the dead are members of its security forces.

Three Israeli civilians and one soldier have also died in the rocket attacks, which have reached deeper into Israel than ever before, bringing one-eighth of Israel's population of 7 million within rocket range.

The mosque destroyed Friday was known as a Hamas stronghold, and the army said it was used to store weapons. It also was identified with Nizar Rayan, the Hamas militant leader killed Thursday when Israel dropped a one-ton bomb on his home.

The explosion killed 20 people, including all four of Rayan's wives and 10 of his children. The strike on Rayan's home obliterated the four-story apartment building and peeled off the walls of others around it, carving out a vast field of rubble.

Israel's military said the homes of Hamas leaders are being used to store missiles and other weapons, and the hit on Rayan's house triggered secondary explosions from the stockpile there.

Rayan, 49, ranked among Hamas' top five decision-makers. A professor of Islamic law, he was known for his close ties to the group's military wing and was respected in Gaza for donning combat fatigues and personally participating in clashes against Israeli forces. He sent one of his sons on an October 2001 suicide mission that killed two Israeli settlers in Gaza.

Israel's military says the homes of Hamas leaders are being used to store missiles and other weapons, and it said the hit on Rayan's house triggered secondary explosions from the stockpile there.

Israeli defense officials said the military had called Rayan's home and fired a warning missile before destroying the building. That was impossible to confirm. The officials spoke on condition of anonymity because they were not authorized to discuss military tactics.

Israel has targeted Hamas leaders many times in the past, but halted the practice during a six-month truce that expired last month.

Hamas is listed as a terrorist organization by the United States and many other Western nations. From 2000 to 2004, Hamas was responsible for killing nearly 400 Israelis and wounding more than 2,000 in 425 attacks, according to the Israeli Ministry of Foreign Affairs.

From 2001 through May 2008, Hamas launched more than 3,000 Qassam rockets and 2,500 mortar attacks against Israeli targets.

Most of Hamas' leaders went into hiding at the start of Israel's offensive. Rayan, however, was known for openly defying Israel and in the past had led crowds to the homes of wanted Hamas figures — as if daring Israel to strike and risk the lives of civilians.

The offensive has not halted rocket fire at Israel, and a barrage landed in the city of Ashkelon early Friday. Two rockets hit apartment buildings, lightly wounding one man, police said. Sirens warning Israelis to take cover when military radar picks up an incoming rocket have helped reduce casualties in recent days.

The military said aircraft destroyed the three rocket launchers used to fire at Ashkelon.

Israel has been building up artillery, armor and infantry on Gaza's border in an indication the punishing air assault could continue with a ground incursion. At the same time, international pressure is building for a cease-fire that would block more fighting.

Israel appears to be maintaining an opening for the intense diplomatic efforts by leaders in the Middle East and, saying it would consider a halt to the fighting if international monitors were brought in to track compliance with any truce with Hamas.

Concerned about protests, Israeli police stepped up security and restricted access to Friday prayers at Jerusalem's al-Aqsa Mosque, barring all males under 50 from entering.

"We condemn these measures, and we believe they contradict the principle of freedom of worship," said Jerusalem's mufti, Mohammed Hussein.

Prayers in Jerusalem ended without incident, though in a nearby east Jerusalem neighborhood youths clashed with anti-riot police on horseback. There were no injuries reported.

The army also imposed a closure on the West Bank, barring nearly all of the area's more than 2 million Palestinians from entering Israel.

Thousands demonstrated in the West Bank in solidarity with the people of Gaza. Palestinian police loyal to Hamas' moderate rival, Palestinian President Mahmoud Abbas, barred protesters from chanting pro-Hamas slogans or waving Hamas banners. Three Hamas activists were arrested.

The Associated Press contributed to this report.