Updated at 3:02 p.m. ET: GAZA CITY, Gaza Strip -- The leader of Hamas said Monday it was up to Israel to end the new conflict it had started, adding that a "land war" would cost Israeli Prime Minister Benjamin Netanyahu the election.

"[Netanyahu] can do it, but he knows that it will not be a picnic and that it could be his political death and cost him the elections," Khaled Meshaal, exiled leader of Hamas, told a news conference in Cairo.

"Whoever started the war must end it," Meshaal said, adding that Netanyahu, who faces an election in January, had asked for a truce, an assertion a senior Israeli official described as untrue.

For its part, Israel said that while it was prepared to step up its offensive by sending in troops, it preferred a diplomatic solution that would end Palestinian rocket fire.

Israeli Vice Prime Minister Moshe Yaalon has said that "if there is quiet in the south and no rockets and missiles are fired at Israel's citizens, nor terrorist attacks engineered from the Gaza Strip, we will not attack."

According to a poll by Israel's Haaretz newspaper, 84 percent of Israelis supported the current Gaza assault, but only 30 percent wanted an invasion, while 19 percent wanted their government to work on securing a truce soon.

Acting as a mediator, Egypt said Monday that a deal for a truce to end the fighting could be close, as Israel bombed dozens of suspected guerrilla sites in the densely populated Hamas-ruled Gaza Strip in its campaign to quell militant rocket fire menacing nearly half of Israel's population.

Twelve Palestinian civilians and four fighters were killed in the sixth day of fighting, local officials said, raising the number of Palestinian dead to 101, the Hamas-run Health Ministry told Reuters, listing 24 children among them. Hospital officials in Gaza said more than half of those killed were non-combatants. Three Israeli civilians died on Thursday in a rocket strike and dozens others have been wounded.

Slideshow: Israel, Gaza violence escalates

Ammar Awad / Reuters

Two sides exchange deadly airstrikes, rocket attacks.

Launch slideshow

Among the targets struck in Gaza City Monday was the Al Shorouq media building, which Israeli warplanes hit for the second straight day. The attack targeted a second-floor apartment used by a leading Islamic Jihad militant. He was killed and four others were injured, NBC News' Ayman Mohyeldin reported.

The Israeli military said it targeted only the floor used by the militants. “The senior [Islamic Jihad] cadre was operating in a media building. They weren’t there to be interviewed. They were using reporters as human shields,” it said on Twitter.

But the lower floors of the building caught fire, trapping journalists on the higher levels. Firefighters were trying to put out the blaze and get the journalists out of the building. The Hamas TV station is located on the top floor.

Family mourned
Thousands turned out on Gaza's streets Monday to mourn four children and five women, who were among the 11 people killed in an Israeli strike that flattened a three-story home the previous day.

The bodies were wrapped in Palestinian and Hamas flags. Echoes of explosions mixed with cries of grief and defiant chants of "God is greatest."

Israel said it was investigating the strike that brought the home crashing down on the al-Dalu family, where the dead spanned four generations. Some Israeli newspapers said the wrong house may have been mistakenly targeted.

Since Wednesday, 877 rockets have been fired from Gaza toward Israel, the Israeli military said Monday. Of those, 570 rockets have struck Israel while the country’s air defense system has intercepted 307, according to the military. Forty-five rockets were fired at southern Israel on Monday, causing no casualties, police said.

Israel's decision to step up targeted attacks on leaders in Gaza on Sunday marked a new and risky phase of the operation, given the likelihood of civilian casualties in the crowded territory of 1.6 million Palestinians.

Negotiations inch forward
International efforts to wrest a cease-fire from the two sides has intensified despite the escalated hostilities. The failure to end the fighting could touch off an Israeli ground invasion, for which thousands of soldiers, backed by tanks and armored vehicles, have already been mobilized and dispatched to Gaza's border.

Leading cease-fire mediation efforts is Egypt, which borders both Israel and Gaza and whose Islamist-rooted government has been hosting leaders of Hamas.

“I strongly urge the parties to cooperate with all efforts led by Egypt to reach an immediate cease-fire," U.N. Secretary-General Ban Ki-moon said before leaving for Egypt. He visits Israel on Tuesday.

European Union governments also said they supported Egyptian efforts to mediate.

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On Sunday, President Barack Obama said it would be "preferable" to avoid a move into Gaza, but that Israel had a right to self-defense and no country would tolerate missiles raining down on its citizens.

Egyptian Foreign Minister Mohamed Kamel Amr, Arab League chief Nabil Elaraby and several other Arab foreign ministers will visit Gaza on Tuesday to show solidarity with Palestinians. Turkish Foreign Minister Ahmet Davutoglu will accompany them, officials said.

Mohammed Saber / EPA

A Palestinian woman inspects the rubble of her destroyed house after an Israeli airstrike in the eastern part of Gaza City on Monday.

Forces gather
Israel launched the current offensive Wednesday after months of intensifying rocket fire from the Gaza Strip, which continued despite the strikes.

Israeli tanks, artillery and infantry have massed in field encampments along the sandy, fenced-off border and military convoys moved on roads in the area. Israel has also authorized the call-up of 75,000 military reservists, so far mobilizing around half that number.

Overnight, aircraft targeted about 80 militant sites, including underground rocket-launching sites, smuggling tunnels and training bases, as well as command posts and weapons storage facilities located in buildings owned by militant commanders, the military said Monday in a release.  

Aircraft and gunboats joined forces to attack police headquarters, and rocket squads were struck as they prepared to fire, the release said.

In all, more than 1,000 Gaza targets have been struck since the operation began.

Some Hamas rockets reached as far as Tel Aviv, Israel's commercial capital, but were shot down by the country's air defense system.

As a precaution against the rocket interceptions endangering nearby Ben-Gurion International Airport, civil aviation authorities said on Monday new flight paths were being used.

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Israel's declared goal is to deplete Gaza arsenals and force Hamas to stop rocket fire that has bedeviled Israeli border towns for years. The rockets now have greater range, putting Tel Aviv and Jerusalem within their reach -- a strategic weapon for Gaza's otherwise massively outgunned guerrillas.

Lior Mizrahi / Getty Images

Israeli soldiers prepare their weapons in a deployment area near the Gaza border on Monday.

NBC News' Ayman Mohyeldin, The Associated Press and Reuters contributed to this report.

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