Tyler Hicks/The New York Times
GAZA CITY — Israel broadened its assault on the Gaza Strip on Saturday from mostly military targets to centers of government infrastructure, obliterating the four-story headquarters of the Hamas prime minister with a barrage of five bombs before dawn.
The attack, one of several on government installations, came a day after the prime minister, Ismail Haniya, hosted his Egyptian counterpart in that very building, a sign of Hamas’s new legitimacy in a radically redrawn Arab world. That stature was underscored Saturday by a visit to Gaza from the Tunisian foreign minister and the rapid convergence in Cairo of two Hamas allies, the prime minister of Turkey and the crown prince of Qatar, for talks with the Egyptian president and the chairman of Hamas on a possible cease-fire.
But as the fighting ended its fourth day, with Israel continuing preparations for a ground invasion, the conflict showed no sign of abating. Gaza militants again fired long-range missiles at Tel Aviv, among nearly 60 that soared into Israel on Saturday. Israel said it hit more than 200 targets overnight in Gaza, and continued with afternoon strikes on the home of a Hamas commander and on a motorcycle-riding militant.
The White House reiterated its strong support for Israel, with Ben Rhodes, the deputy national security adviser, describing rocket fire from Gaza as “the precipitating factor for the conflict.”
“We believe Israel has a right to defend itself, and they’ll make their own decisions about the tactics that they use in that regard,” Mr. Rhodes told reporters on Air Force One en route to Asia.
Hamas health officials said 45 Palestinians had been killed and 385 wounded since Wednesday’s escalation in the cross-border battle. In Israel, 3 Israeli civilians have died and 63 have been injured. Four soldiers were also wounded on Saturday.
Two rockets were fired at Tel Aviv on Saturday. One landed harmlessly, probably at sea. The other was intercepted by the Iron Dome defense system in the sky above the city. An Iron Dome antimissile battery had been hastily deployed near the city on Saturday in response to the threat of longer-range rockets.
Since Wednesday, Iron Dome has knocked 245 rockets out of the sky, the military said, while 500 have struck Israel. The American-financed system is designed to intercept only rockets streaking toward towns and cities and to ignore those likely to strike open ground.
There have been failures — on Saturday a rocket crashed into an apartment block in the southern port city of Ashdod, injuring five people — but officials have put its success rate at 90 percent.
Analysts said there is no clear end to the conflict in sight, since Israel neither wants to re-engage in Gaza nor to eliminate Hamas and leave the territory to the chaos of more militant factions.
“Ultimately,” said Efraim Halevy, a former chief of Israel’s intelligence service, “both sides want Hamas to remain in control, strange as it sounds.”
But Mkhaimar Abusada, a political science professor at Al Azhar University here, cautioned that “there is no military solution to the Gaza problem.”
“There has to be a political settlement at the end of this,” he said. “Without that, this conflict is just going to go on and on.”
President Mohamed Morsi of Egypt said late Saturday night that “there could be a cease-fire soon,” after he and other members of his government spent the day in meetings with the Turkish premier, the Qatari prince, the political leaders of Hamas and other Gaza factions. But Mark Regev, a spokesman for Prime Minister Benjamin Netanyahu of Israel, denied reports that a truce was imminent.
It was unclear whether the deal under discussion would solely suspend the fighting or include other issues. Hamas — which won elections in Gaza in 2006 and took full control in 2007 but is considered a terrorist organization by Israel and the United States — wants to turn its Rafah crossing with Egypt into a free-trade zone and seeks Israel’s withdrawal from the 1,000-foot buffer it patrols on Gaza’s northern and eastern borders.
Mr. Rhodes said the Turkish and Egyptian leaders “have the ability to play a constructive role in engaging Hamas and encouraging a process of de-escalation.”
Mr. Netanyahu, for his part, spoke Saturday with the leaders of Britain, Germany, Italy, Greece, Poland, Portugal, Bulgaria and the Czech Republic, according to a statement from his office.