Israel Air Force warplanes stepped up airstrikes on the northern Gaza Strip on Saturday, bombing more than 40 Hamas targets over the course of the day and killing the third senior Hamas official since Israel's aerial assault began last Saturday.

Abu Zakaria al-Jamal, a commander of the Hamas armed wing, died of wounds sustained in an airstrike overnight.

On Saturday morning, Israel Radio quoted a spokesman for the Hamas military wing as saying it had repelled an attempt by Israel Defense Forces soldiers to infiltrate the Shajaiyeh section of Gaza City.

According to Israel Radio, Hamas said that its militants detected the soldiers and fired six mortar shells. Hamas said the soldiers reportedly opened fire and then returned to Israeli territory.

On Friday, the IAF bombed the home of Hamas member Mohammed Madhoun, who was responsible for rocket attacks against Israel.

Madhoun's house was also used as a laboratory for the manufacturing of rockets and explosive devices and as a storage facility for rockets, mortar shells, and various weapons.

At least eight people, among them five children, have been killed in Israeli airstrikes in Gaza on Friday. In all, the IAF reportedly hit 35 Hamas targets throughout the day Friday.

Earlier Friday, the IAF targeted the home of Hamas military wing commander Imad Akel, a senior Hamas operative. His house was used as a large storage facility for weapons. Akel was the founder and one of the men heading Hamas' rocket and mortar efforts, in addition to being a weapons manufacturer. Large secondary explosions were seen following the attack proving the presence of large amounts of weaponry.

The IAF also bombed the residence of former Hamas minister Atef Adwan. Adwan was the Minister of Prisoner Affairs in the government of Hamas leader Ismail Haniyeh.

Also on Friday afternoon, the IAF resumed its assault on the Philadelphi route tunnels, used to smuggle supplied into the Strip from Egypt.

Earlier Friday, IAF planes, in coordination with the Shin Bet, bombed the home of senior Hamas activist Mohammed Matouk. The IDF said that Matouk's home was being used by militants as a weapons storehouse and factory, and that a smuggling tunnel had been dug underneath the building.

Before dawn, Israeli aircraft hit 15 houses belonging to Hamas militants, Palestinians said. They said the Israelis either warned nearby residents by phone or fired a warning missile to reduce civilian casualties.

Late Thursday, IAF aircraft struck a mosque in the Jabaliya refugee camp in the Gaza Strip, being used as a terror-hub by the Hamas terror organization.

The mosque had served as a storehouse for a large number of Grad missiles, Qassam rockets and additional weaponry. The strike set off series of secondary explosions and a large fire, caused by the ammunitions stockpiled inside the mosque.

The mosque had also served as a center of operations for Hamas, as a meeting place for its operatives and a staging ground for terror attacks, the Israel Defense Forces spokesperson's office said in a statement.

"The IDF will continue to attack any target used for terrorist activity, and will not hesitate to strike those involved in terrorism against the citizens of the State of Israel, even if they deliberately choose to operate from locations of religious or cultural significance," the statement went on to say.

Earlier Thursday, an Israeli aircraft killed a high-ranking Hamas official in Gaza along with nine women, including at least four wives, and 11 of his children, in the first major assassination since the IDF launched Operation Cast Lead on Saturday.

According to sources from the defense establishment, decision-makers are increasingly inclined to order a ground invasion into Gaza.

The assassination of Nizar Ghayan left dozens of people from neighboring buildings injured and brought up the body count on the Palestinian side to 425 people since the start of the campaign. The number of wounded is now estimated at around 2,000.

The IDF Spokesman said that Ghayan's house had served as a weapons silo and a war room for Hamas. Under the house, according to the IDF, was a tunnel which was meant to serve as an escape route in case of an Israeli attack.

Palestinian media reported that the incident was not a planned assassination, but rather a routine bombing of a target suspected by the IDF to contain weapons.

The IDF has code named such operations "roof knocking," in which the army informs the residents of s suspected building that they have 10 minutes to leave the premises. In some cases, residents of suspected houses have been able to prevent bombing by climbing up to the roof to show that they will not leave, prompting IDF commanders to call off the strike. In these cases, Channel 10 reported Thursday, the IAF sometimes launches a relatively harmless missile at the corner of the roof, avoiding casualties but successfully dispersing the crowd.

Sources familiar with Ghayan's record said he was one of the people who encouraged Gazans to climb on rooftops to prevent bombings.

It appears that the "roof knocking" technique was used in the assassination, but Ghayan decided to stay indoors with his family, and the army opted to bomb the house anyway.

A lecturer at Gaza's Islamic University, Ghayan, 49, had mentored suicide bombers and would sometimes go on patrol with Hamas fighters. 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.

He was also an outspoken advocate of renewing suicide bombings against Israel. Hamas said Israel would pay a "heavy price" for his death. Ghayan was one of the most extreme opponents of Fatah, and supported violence against Fatah's men during Hamas' seizure of power.

Foreign Minister Tzipi Livni rejected calls for a 48-hour "humanitarian pause" and told her French counterpart, Bernard Kouchner, that Hamas must not be given the opportunity to gain any sort of legitimacy within a renewal of a truce. Under the current offensive, she said, Hamas understand that Israel will not tolerate Gaza rocket fire without response.

In addition to the assassination, the Israel Air Force bombed several other Hamas targets.

Hamas fired about a dozen rockets into Be'er Sheva and near Ashdod, resulting in no injuries. In all, Gaza militants fired at least 50 rockets at southern Israel throughout the day Thursday.

Awaiting a decision by the political leadership, ground forces of the IDF are in the final stages of preparations for an invasion into Gaza, and the army has amassed the forces outside the Strip in formation for a rapid deployment in the area as soon as the order is given.

But even as IDF tanks rev their engines, various international powers are offering to broker a cease-fire between Hamas and Israel. The IDF is recommending a major, but relatively short-term, ground offensive in the Gaza Strip.