Updated

Israeli airstrikes in the Gaza Strip intensified Saturday evening and tanks began repositioning themselves around the border despite international efforts to secure a cease-fire and avert a ground war between Israel and Hamas.

Most of the latest airstrikes hit empty buildings and abandoned sites, suggesting Israel may be running out of targets — though artillery units joined the Gaza for the first time Saturday, and a mosque was hit, killing 10 people.

The latest developments came after senior leadership in Israel gave the thumbs up for a ground invasion of Gaza, sources told FOX News. Such action is looking increasingly likely and may happen soon, as Israeli tanks began moving along the border Saturday night.

Click here for photos. (Warning: Graphic Content)

Israeli defense officials said some 10,000 troops, including tank, artillery and special operations units, were massed on the Gaza border and prepared to invade. The officials told the Associated Press that top commanders are split over whether to send in ground forces, in part because such an operation could lead to heavy casualties but also because they believe Hamas already has been dealt a heavy blow. The officials spoke on condition of anonymity because they were classified discussions.

Israel launched the aerial campaign a week ago 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.

The Jerusalem Post reported Saturday that Hamas declared its members foiled an attempt by Israeli forces to move within the Gaza Strip, an incident that Israeli forces, however, claimed the "incident never happened."

French President Nicolas Sarkozy is visiting the region next week, and U.S. President Bush and U.N. chief Ban Ki-moon both spoke in favor of an internationally monitored truce.

But Hamas, in its first reaction to the proposal on Saturday, seemed cool to the idea of international monitors.

Early Saturday, Israel dropped leaflets in downtown Gaza City ordering people off the streets.

Israeli warplanes and gunboats blasted more than two dozen Hamas, including weapons storage facilities, training centers and leaders' homes as Israel's offensive against Gaza's Islamic militant rulers entered a second week.

Airstrikes reportedly killed Abu Zakaria al-Jamal, a senior leader of the armed wing of the militant group, which is listed as a terrorist organization by the United States and many other Western nations.

Palestinian militants fired six rockets into southern Israel, causing no injuries. One rocket struck a house in the city of Ashkelon, police said.

President Bush, in a radio address taped Friday, accused Hamas of an "act of terror" in its rocket attacks into Israel and suggested that no cease-fire would be acceptable without monitoring to halt the flow of weapons to terrorist groups.

From 2001 through May 2008, Hamas launched more than 3,000 Qassam rockets and 2,500 mortar attacks against Israeli targets, and on Friday, exiled Hamas leader Khaled Meshaal said from Damascus that his group was prepared for an invasion and could abduct soldiers, as it has in the past, if Israel attempts the incursion.

Israel launched the new round of airstrikes on Gaza in response to renewed missile attacks by Hamas after the two sides' six-month cease-fire ended last month. A ground invasion of the territory has looked increasingly likely, as Israel has been bringing artillery, armor and infantry to the border.

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.

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

FOX News' Mike Tobin and the Associated Press contributed to this report.