JERUSALEM (AP) -- Israel offered to suspend its offensive in the Gaza Strip on Friday during a brief visit by Egypt‘s premier there if militants refrain from firing rockets at Israel, an official said, but the Palestinians unleashed a fresh salvo.

An official in Prime Minister Benjamin Netanyahu’s office said the Israeli leader was responding to an Egyptian request.

Gaza militants stepped up their barrages of rocket fire into Israel as Hesham Kandil crossed into Gaza before midday through the only border post with Egypt, heavily guarded by Egyptian security personnel wearing flak jackets and carrying assault rifles.

He was greeted by Gaza‘s Hamas prime minister, Ismail Haniyeh, who ventured out in public for the first time since Israel launched the offensive Wednesday by assassinating the militant group’s military commander.

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 Israeli 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.

There were no immediate reports of Israeli retaliation for the latest salvo. Israeli police spokesman Micky Rosenfeld said the militants were making a clear statement. "There’s no intention whatsoever to stop firing into Israel," he said.

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.

Egypt said Kandil‘s three-hour visit Friday was meant as a show of solidarity with the Palestinian territory’s militant Hamas rulers.

Egyptian intelligence officials involved in negotiations to end previous rounds of fighting are accompanying Kandil on his visit, an Egyptian diplomat said, suggesting it was more than a display of support.

The diplomat said Gaza militants have 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.

Word of the possible pause in the fighting came 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.

Israeli troops, tanks and armored personnel carriers massed near the Palestinian territory, signaling a ground invasion might be imminent.

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. No casualties were reported there, but three people died in the country’s rocket-scarred south when a projectile slammed into an apartment building.

The death toll in Gaza was 19, including five children, according to Palestinian health officials.

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 Haniyeh’s home, signaled that Israel was expanding its offensive beyond military targets.

Ten-month-old Haneen Tafesh was killed Thursday when flying shrapnel from an air attack on a field next to her family‘s shack struck her in the head.

"What did she do? Did she fire any rockets?’‘ asked her 23-year-old father, Khaled Tafesh, as he waited outside the Shifa hospital morgue in Gaza City, waiting for the funeral of his only child to begin.

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 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.