Israel targeted the home of the top Hamas leader in the Gaza Strip on Tuesday in some of the heaviest bombardment of the ongoing conflict after Prime Minister Benjamin Netanyahu warned his country to be prepared for a prolonged campaign.

Palestinian officials said Israel also hit a fuel tank at Gaza’s only electricity plant early Tuesday, forcing it to shut down. The attack left the Palestinian territory’s 1.8 million residents with no electricity or running water and opened the possibility of an even graver humanitarian crisis.

“The missile which targeted the power plant actually targeted 1.8 million Palestinians,” said Jamal Dardasawi, a spokesman for Gaza’s electricity distribution department. “It is the most awful missile attack of the whole war. They have caused a catastrophic humanitarian situation.”

Capt. Eytan Buchman, an Israeli army spokesman, said the military could not yet confirm whether its forces had struck the power plant.

Gaza Health Ministry officials said the Israeli attacks from early Tuesday to early Wednesday killed 128 Palestinians, pushing the death toll on the Palestinian side to 1,229. The United Nations said about 70 percent of those killed were civilians.

Expanding its list of targets, Israel destroyed the family home of Ismail Haniyeh, the top leader of the Islamist militant group that controls Gaza. Other airstrikes hit Hamas’s al-Aqsa television broadcast center, a finance building and the homes of local mayors. Haniyeh is in hiding and his whereabouts are unknown, but he has delivered prerecorded televised addresses.

Along the coast of the tiny seaside enclave, Israel also hit a fishing harbor, causing hotels where scores of international journalists are staying to shake. Airstrikes also hit the Rafah area, along Gaza’s border with Egypt, according to local news reports.

In the sprawling Jebaliya refugee camp in northern Gaza, at least 24 people — 10 of them from the same family — were killed and dozens wounded in a barrage of tank fire early Wednesday, the Associated Press reported, citing Hamas health officials.

Israel said Tuesday afternoon that its forces had come under attack from militants in Gaza emerging from a concealed tunnel. A gun battle followed, although no details were immediately available. The Israeli military reported a similar infiltration Monday evening, saying five soldiers were killed in a battle with militants from Gaza who entered southern Israel via a tunnel. At least one militant died.

The deaths of the five soldiers brought the number of Israeli troops killed in the three-week-old conflict to 53, the largest toll since Israel’s 2006 war with Lebanon. Mortar and rocket attacks from Gaza have also killed two Israeli civilians and a Thai worker.

Rocket barrages from Gaza sent people in Tel Aviv, Israel’s commercial capital, scurrying to shelters early Tuesday.

In the center of Gaza City, an airstrike obliterated al-Amin Mohammed Mosque opposite the Gaza home of Palestinian Authority President Mahmoud Abbas. In 2007, when it seized control of Gaza, Hamas took over the home and used it to house senior leaders. The militants handed it back to Abbas earlier this year after Hamas and the Palestinian Authority reached an agreement on forming a unity government.

Satellite images released by the United Nations show the impact of Israeli strikes on structures in Gaza. One of the most ravaged areas is the Shijaiyah neighborhood in the southeastern part of Gaza City. (The Washington Post/The Washington Post)

Neighbors said that the mosque was not Hamas-run and that anyone could pray there.

“This is a mosque for the public, and I am one of the public,” said Muhammed Abdu, a 45-year-old engineer, as he looked at a cavernous hole filed with debris where the mosque had stood. “This is all part of a strategy to burn Gaza down.”

He said the attack underscored the need for a cease-fire. But like many Gazans interviewed over the past two days, Abdu said the core Palestinian demand of lifting an economic blockade by Israel and Egypt should be met.

“To bring milk in for your child, is that a crime?” Abdu asked. “To have an open crossing so that you can leave for medical care, is that a crime? To travel outside for your business, is that a crime?”

Near the Nusairat refu­gee camp, in the middle of the Gaza Strip, the shattered fuel tank of the territory’s primary power plant continued to emit flames and thick plumes of smoke hours after being hit.

The plant is Gaza’s primary source of electricity, powering sewage treatment systems, water pumps and hospitals, said Dardasawi, the Palestinian official. It is especially important, he added, because six of eight electricity supply lines that run from Israel were damaged. Egypt also supplies some electricity, he added, but hardly enough to power the border town of Rafah.

“This is like a time bomb,” said Dardasawi, referring to the potential humanitarian crisis.

Outside Haniyeh’s wrecked house in the Beach Camp neighborhood of Gaza City, neighbors gathered Tuesday to express anger. Not far away, 10 people, including seven children, were killed in an attack Monday that Hamas and Israel blamed on each other.

Neighbors said Haniyeh and his family had not lived in the house since the conflict erupted. The dwelling, they said, was hit around 2 a.m., and no one was killed or injured. Israel’s military, they said, phoned a neighbor around 1:45 a.m. with instructions to tell other residents on the street to evacuate.

But most fled when they heard two small missiles from an Israeli drone strike the house, presumably as a warning, residents said. Minutes later, a powerful airstrike, possibly from an Israeli F-16, brought down the house in a pinpoint attack that did little serious damage to the surrounding homes in this densely packed enclave.

Some neighbors said Tuesday that the attack made them support Hamas even more and that they would never accept a cease-fire until Palestinian demands were met.

“Israel said it wouldn’t target him because he is a politician,” said Wasifiyah Hassonehm, 53, who lives two houses down. “Now, they are targeting everyone — the politicians, the civilians, everyone.”

In an e-mailed statement to journalists, Haniyeh said the attack would not deter Hamas. “Destroying our homes will not change our attitude, but it will strengthen it,” he said.

Booth and Eglash reported from Jerusalem. Daniela Deane in Rome contributed to this report.