Updated 3:56 a.m. Eastern
JERUSALEM Israel said its air force bombed the house of a Hamas commander in the Gaza Strip after militants fired more than a dozen rockets toward southern Israel, trampling hopes for a three hour ceasefire during a brief visit by Egypt's premier to the tiny stretch of land.
Israel had agreed to halt it's three-day assault on Hamas in the Gaza Strip if militants refrained from firing rockets at Israel. It would have been the first break in the escalating conflict.
"Hamas does not respect the Egyptian prime minister's visit to Gaza and violates the temporary ceasefire that Israel agreed to during the visit," Ofir Gendelman, a spokesman for the Israeli Prime Minister wrote on Twitter, according to Reuters.
An official in Netanyahu's office said the ceasefire had been agreed to after a request from Egypt.
Israel told the Egyptians the military "would hold its fire on the condition that during that period, there won't be hostile fire from Gaza into Israel," the official said. "Prime Minister Netanyahu is committed to the peace treaty with Egypt, which is in the strategic interest of both countries, he added, speaking on condition of anonymity to discuss the diplomatic exchange.
It wasn't clear whether Israel had hoped to use the possible suspension of hostilities to seek a broader truce or had agreeing to the halt in fighting only as a gesture to Egypt.
Three days of fierce fighting between Israel and Gaza militants has widened the instability gripping the region, straining already frayed Israel-Egypt relations. The Cairo government recalled its ambassador in protest and sent its prime minister, Kandil, to Gaza in a show of solidarity with the Palestinian territory's militant Hamas rulers.
New agencies including AFP, Al-Arabiya, and Al-Jazeera reported early Friday that Kandil had arrived in Gaza.
Egyptian intelligence officials involved in negotiations to end previous rounds of fighting are accompanying Kandil on his visit, an Egyptian diplomat said, suggesting it is more than a display of support.
The diplomat said Gaza militants had told Egyptian intelligence officials they would be willing to hold their fire if Israel would commit to mediation to stop its military operation and targeted killings.
The very brief pause in the fighting was shattered after a night of fierce exchanges and signals that Israel might be preparing to invade Gaza. Overnight, the military said it targeted about 150 of the sites Gaza gunmen use to fire rockets at Israel, as well as ammunition warehouses, bringing to 450 the number of sites struck since the operation began Wednesday.
CBS News correspondent Allen Pizzey reports that Israeli troops, tanks and armored personnel carriers had begun massing near the Gaza border -- signaling a possible ground invasion in the coming hours or days.
Militants unleashed dozens of rocket barrages overnight.
Fighting between the two sides escalated sharply Thursday with a first-ever rocket attack from Gaza on the Tel Aviv area, menacing Israel's most densely populated area. Pizzey said at least two rockets hit in the Tel Aviv area, but no casualties were reported. Three people died in the country's rocket-scarred south, however, when a projectile slammed into an apartment building earlier in the day.
CBS News' Michal Ben-Gal reports that Jerusalem was also put on high alert Friday morning, with many police deployed in the city's predominantly Arab eastern side to prevent clashes after the Islamic Friday prayers.
The death toll in Gaza climbed to 19, including five children, according to Palestinian health officials, as waves of Israeli fighter planes and drones sent missiles hurtling down on suspected weapons stores and rocket-launching sites.
Early Friday, 85 missiles exploded within 45 minutes in Gaza City, sending black pillars of smoke towering above the coastal strip's largest city. The military said it was targeting underground rocket-launching sites.
One missile flattened sections of the Interior Ministry, leaving a huge pile of rubble, and another hit an uninhabited house belonging to a senior Hamas commander. Those strikes, together with an attack on a generator building near the home of Gaza's Hamas prime minister, Ismail Haniyeh, signaled that Israel was expanding its offensive beyond military targets.
Israel and Hamas had largely observed an informal truce since Israel's devastating incursion into Gaza four years ago, but rocket fire and Israeli airstrikes on militant operations continued sporadically. The latest flare-up exploded into major violence Wednesday when Israel assassinated Hamas' military chief, following up with a punishing air assault meant to cripple the militants' ability to terrorize Israel with rockets.
The Israeli offensive has not deterred the militants from firing more than 400 rockets aimed at southern Israel, the military said. On Thursday, they also unleashed for the first time the most powerful weapons in their arsenal -- Iranian-made Fajr-5 rockets capable of reaching Tel Aviv.
The two rockets that struck closest to Tel Aviv appear to have landed in the Mediterranean Sea, defense officials said, and another hit an open area on Tel Aviv's southern outskirts.
No injuries were reported, but the rocket fire sowed panic in Tel Aviv and made the prospect of a ground incursion more likely. The government later approved the mobilization of up to 30,000 reservists for a possible invasion.
Netanyahu said the army was hitting Hamas hard with what he called surgical strikes, and warned of a "significant widening" of the Gaza operation. Israel will "continue to take whatever action is necessary to defend our people," said Netanyahu, who is up for re-election in January.
At least 12 trucks were seen transporting tanks and armored personnel carriers toward Gaza late Thursday, and buses carrying soldiers headed toward the border area.
An Israeli ground offensive could be costly to both sides. In the last Gaza war, Israel devastated parts of the territory, setting back Hamas' fighting capabilities but also paying the price of increasing diplomatic isolation because of a civilian death toll numbering in the hundreds.
The current round of fighting is reminiscent of the first days of that three-week offensive against Hamas. Israel also caught Hamas off guard then with a barrage of missile strikes and threatened to follow up with a ground offensive.
Much has changed since then.
Israel has improved its missile defense systems, but it is facing a more heavily armed Hamas. Israel estimates the militants have 12,000 rockets, including more sophisticated weapons from Iran and from Libyan stockpiles plundered after the fall of Moammar Gadhafi's regime there last year.
Also, regional alignments have changed dramatically since the last Gaza war. Hamas has emerged from its political isolation as its parent movement, the region-wide Muslim Brotherhood, has risen to power in several countries in the wake of last year's Arab uprisings, particularly in Egypt.
At the same time, while relations with Israel have cooled since the toppling of longtime Egyptian leader Hosni Mubarak, Islamist President Mohammed Morsi has not brought a radical change in Egypt's policy toward Israel. He has promised to abide by Egypt's 1979 peace deal with Israel and his government has continued contacts with Israel through its non-Brotherhood members.