GAZA CITY -- Israeli forces killed at least 11 people, including several children, in a single airstrike that destroyed a home here on Sunday, as Israel pressed its bombardment of the Gaza Strip for a fifth day, deploying warplanes and naval vessels to pummel the coastal enclave.
The airstrike, which the Israeli military said was meant to kill a Palestinian militant involved in the recent rocket attacks, was the deadliest operation to date and would no doubt weigh on negotiations for a possible cease-fire. Among the dead were five women and four small children, The Associated Press reported, citing a Palestinian health official.
Two media offices were also hit on Sunday, and Prime Minister Benjamin Netanyahu of Israel warned of a "significant" expansion in the onslaught, which has already killed over 50 people, many of them civilians.
Speaking on Sunday from Bangkok, President Obama condemned missile attacks by Palestinian fighters in Gaza and defended Israel's right to protect itself.
"There's no country on earth that would tolerate missiles raining down on its citizens from outside its borders," Mr. Obama said in his first public comments since the violence broke out. "We are fully supportive of Israel's right to defend itself."
The president also said that efforts were under way to address Israel's security concerns and end the violence. "We're going to have to see what kind of progress we can make in the next 24, 36, 48 hours," Mr. Obama said.
Even as the diplomacy intensified on Sunday, the attacks continued in Gaza and Israel.
Mr. Netanyahu made his warning as militants in Gaza aimed at least one rocket at Tel Aviv, a day after Israeli forces broadened the attack beyond military targets, bombing centers of government infrastructure in Gaza, including the four-story headquarters of the Hamas prime minister.
"We are exacting a heavy price from Hamas and the terrorist organizations, and the Israel Defense Forces are prepared for a significant expansion of the operation," Mr. Netanyahu told his cabinet at its routine Sunday meeting, referring directly to the of thousands of reservists who have been called up and the massing of armor on the Gaza border that many analysts have interpreted as preparations for a possible invasion.
"I appreciate the rapid and impressive mobilization of the reservists who have come from all over the country and turned out for the mission at hand," Mr. Netanyahu said. "Reservist and conscript soldiers are ready for any order they might receive."
His remarks were reported shortly after a battery of Israel's Iron Dome defense shield, hastily deployed near Tel Aviv on Saturday in response to the threat of longer-range rockets, intercepted at least one aimed at the city on Sunday, Israeli officials said. It was the latest of several salvos that have illustrated Hamas's ability to extend the reach of its rocket attacks.
Since Wednesday, when the escalation of the conflict began, Iron Dome has knocked 245 rockets out of the sky, the military said Saturday, 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. But on Sunday a rocket fired from Gaza plowed through the roof of an apartment building in the southern Israeli city of Ashkelon. There were no immediate reports of casualties there.
In Gaza City, the crash of explosions pierced the quiet several times throughout the early morning.
Before the latest deadly strike involving civilians on Sunday, Hamas health officials had said the Palestinian death toll had risen to 53. One of the latest victims was a 52-year-old woman whose house in the eastern part of Gaza City was bombed around lunchtime.
A few hours earlier, a Hamas militant was killed and seven people were wounded in an attack on the Beach Refugee Camp, where Ismail Haniya, the Hamas prime minister, has a home. Those killed on Sunday included three children ages 1 through 5, the health officials said.
In Israel, 3 civilians have died and 63 have been injured. Four soldiers were wounded on Saturday.
The onslaught continued despite talks in Cairo that President Mohamed Morsi of Egypt said Saturday night could soon result in a cease-fire. Mr. Netanyahu said he would consider a comprehensive cease-fire if the launchings from Gaza stopped.
The attack on Mr. Haniya's office, one of several on government installations, came a day after he hosted his Egyptian counterpart in the same 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 trips to Cairo by 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.
A delegation of Arab ministers plans to visit Gaza on Tuesday, Reuters reported, and Ban Ki-moon, the secretary general of the United Nations, is expected in Cairo on Monday.
But Mark Regev, a spokesman for Mr. Netanyahu, denied reports on Saturday that a truce was imminent.
Mr. Obama said Sunday that he had spoken several times with Mr. Netanyahu, Mr. Morsi and Prime Minister Recep Tayyip Erdogan of Turkey in hopes of finding a way to address Israel's security concerns without further ramping up military operations.
"We are actively working with all the parties in the region to see if we can end those missiles being fired without further escalation of violence in the region," he said.
It was unclear whether the deal under discussion in Cairo 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. Netanyahu has also spoken with the leaders of Britain, Germany, Italy, Greece, Poland, Portugal, Bulgaria and the Czech Republic, according to a statement from his office. On Sunday, he said he appreciated the "understanding they are displaying for Israel's right to defend itself."
Some European leaders seemed to be counseling restraint as much as offering support.
The French news media reported that the foreign minister, Laurent Fabius, was heading to Israel to seek a cease-fire, and William Hague, his British counterpart, cautioned that an Israeli invasion of Gaza "would lose Israel a lot of the international support and sympathy they have" and make it "much more difficult to restrict and avoid civilian casualties."
The conflict, meanwhile, showed no sign of abating.
Palestinian news agencies reported that two children were killed in a predawn strike on Sunday in Beit Lahiya in northern Gaza. The Israeli military said it had "targeted dozens of underground launchers" overnight and also hit what it called a Hamas training base and command center. The Israeli Navy "targeted terror sites on the northern Gaza shore line," the statement said, in repeated rounds of missiles.
Among the buildings that Israel hit overnight were two containing the offices of local news media outlets.
Salama Marouf of the Hamas media office condemned what he called an "immoral massacre against the media" and called the attack a confession by Israel "that it has lost the media battle."
Seven journalists were injured in the first attack, around 1:40 a.m., in the Shawa and Hossari Building in downtown Gaza City. It houses two local radio stations -- one run by the militant Islamic Jihad -- and the offices of the Ma'an Palestinian news agency as well as the German broadcaster ARD.
One of the journalists injured on Sunday, Khader Zahar of the Beirut-based Al Quds satellite channel, was said to have lost a leg in the explosion, which hit its 11th-floor studio.
The Israeli military referred to the two sites as "Hamas operational communication sites that were identified by precise intelligence."
"In order to minimize the damage to noninvolved persons, the I.D.F. only targeted the communication devices which were located on the roof of the building, and not the operations room of Hamas that is located on one of the floors," the military said.
"The second site was targeted at approximately 06:50 a.m. and was also part of Hamas's operational communications that was deliberately located on the roof of the building, in which several international media bureaus reside," the military said in a statement.
It urged "international journalists and correspondents who operate in the Gaza Strip carrying out their duties, to stay clear of Hamas's bases and facilities -- which serve them in their activity against the citizens of Israel."
Ayman Amar, a spokesman for the Al Quds television, said seven camera operators and editors were resting on couches in their offices around 1:30 a.m. when a missile fired from an Israeli helicopter ripped through the roof. They fled, and three more bombs dropped around 10 minutes later, Mr. Amar said.
Al Quds, an independent channel with 50 employees in the Gaza Strip, has had offices in the building since 2007, and on its top floor since 2011. Since the conflict escalated, journalists have been working around the clock and catching naps in the office. Some of its employees were back out on the streets on Sunday, Mr. Amar said, and others were trying to clear the wreckage from the five-room editing studio.
"We never expected that it would hit us," he added. "So far we don't know why; there are no reasons. We will not stop. It is our duty toward our cause to support the Palestinian people."
Later, a missile that was dropped from an Apache helicopter hit the top of the 15-story Al Shoruq Building, which is also downtown, witnesses said.
The target was the Hamas channel that broadcasts locally, Al Aqsa, but the building also contains offices of the Al Arabiya television network and the Middle East Broadcast Center, which runs it, as well as the live studio of an Iranian television station and two production companies -- the Gaza Media Center and Mayadeen -- that provide services for Fox News, Sky News, CBS and Al Jazeera.
No one was injured in that attack. Witnesses said that everyone in the building fled after a warning missile was fired in the stairwell, two minutes before the attack on the roof.
The Foreign Press Association in Jerusalem said it was "concerned" by the attacks, recalling a United Nations ruling that "journalists, media professionals and associated personnel engaged in dangerous professional missions in areas of armed conflict shall be considered civilians, to be respected and protected as such."
The ability to gain access to and influence news media coverage is critical to both sides seeking to promote their rival claims and versions of the events and arguments underpinning the conflict, recalling the 2008-9 winter invasion of Gaza that brought international condemnation of Israel.
The news media war took a new turn on Sunday when the Israeli military intercepted and took over signals from two local radio stations -- Al Aqsa and Al Quds -- to broadcast a warning to Gaza residents: "We recommend that you stay away from the places of terrorists and the infrastructure of Hamas."
It continued: "Hamas is playing with fire and putting you at risk."
Israel's Foreign Ministry said on Saturday that 22 foreign journalists were prevented by Hamas from leaving the Gaza Strip.
Jodi Rudoren and Fares Akram reported from Gaza City. Reporting was contributed by Isabel Kershner, Carol Sutherland and Iritz Pazner Garshowitz from Jerusalem; Tyler Hicks from Gaza, Peter Baker from Bangkok, Alan Cowell from London, Michael Schwirtz from New York and David D. Kirkpatrick and Mayy El Sheikh from Cairo.
This article originally appeared in The New York Times.