GAZA CITY, Gaza Strip (AP) — Israel unleashed its heaviest bombardment in a 3-week-old war against Hamas on Tuesday, striking symbols of the militant group's control in Gaza and firing tank shells that Palestinian officials said shut down the strip's only power plant.

The fighting came as diplomatic efforts to forge a truce remained stalled despite a death toll that Palestinian officials said rose above 1,200 on Tuesday. The shadowy leader of the Hamas military wing said his group will not cease fire until its demands are met.

On Tuesday evening, residents of the sprawling Jebaliya refugee camp in northern Gaza reported intense tank shelling. Ten members of an extended family were killed and 50 other people wounded in the area, Palestinian health officials said. Two brothers driving in a car with markings of a U.N. aid agency were killed by shrapnel, an area resident said.

"It was like an earthquake," Moussa al-Mabhouh, a volunteer for Gaza's Civil Defense, said of the scene. "Roofs collapsed, walls cracked and wounded people everywhere."

The heavy strikes — which came a day after Prime Minister Benjamin Netanyahu on Monday warned of a "prolonged" campaign against Hamas — were a new blow to international efforts to reach a sustainable truce in the fighting.

Israel has vowed to stop the Hamas rocket and mortar fire that has reached increasingly deeper into its territory and to destroy a sophisticated network of tunnels that have been used by the militants to infiltrate the Jewish state. For its part, Hamas has so far rejected cease-fire efforts unless its demands are met, including a lifting of a punishing blockade.

The rare remarks by the Hamas military wing's leader, Mohammed Deif, were broadcast late Tuesday on Al-Aqsa TV, the satellite station of Hamas.

"There is not going to be a cease-fire as long as the demands of our people are not fulfilled," he said.

Deif's voice was recognizable in the audio statement. He has survived repeated Israeli assassination attempts and has operated from hiding for years.

Al-Aqsa also broadcast a videotape it said showed an infiltration by Hamas fighters into Israel on Monday through a border tunnel.

At least 1,210 Palestinians have been killed, including 109 on Tuesday, and 7,000 wounded since the start of fighting July 8, said Palestinian health official Ashraf al-Kidra. He said 16 other people died of wounds sustained on previous days.

The dead included multiple members of at least five families who were pulled from the rubble Tuesday after airstrikes and tank shelling struck their homes, including the mayor of a refugee camp and his 70-year-old father, according to Palestinian health officials and the Palestinian Red Crescent.

Israel has reported 53 soldiers and three civilians killed.

Already, the intensity and the scope of the current Gaza operation is on par with an invasion five years ago, which ended with Israel unilaterally withdrawing after hitting Hamas hard.

On Tuesday, Israeli warplanes carried out dozens of attacks, leveling the home of the top Hamas leader in Gaza, Ismail Haniyeh, and damaging the offices of the movement's Al-Aqsa satellite TV station, a central mosque in Gaza City and government offices.

Haniyeh's house, in a narrow alley of the Shati refugee camp, was reduced to rubble but no one was hurt. Residents placed a large framed portrait of Haniyeh atop the wreckage and draped it with green Hamas flags and Palestinian national banners.

Israel has targeted several homes of Hamas leaders but none has been killed — presumably because they have kept a low profile. Haniyeh said in a statement Tuesday that "destroying stones will not break our determination."

The scene at the Gaza power plant after two tank shells hit one of three fuel tanks was daunting and thick black smoke rose into the sky for hours. The station's shutdown further disrupted the supply of electricity and water to the 1.7 million people packed into the narrow Palestinian coastal territory.

"We need at least one year to repair the power plant, the turbines, the fuel tanks and the control room," said Fathi Sheik Khalil of the Gaza Energy Authority. "Everything was burned."

He said crew members who had been trapped by the fire for several hours were evacuated.

Even before the shutdown, Gaza residents only had electricity for about three hours a day because fighting had damaged power lines. Most of the power lines from Israel that provided electricity for payment were previously damaged in the fighting.

This means most of Gaza will now be without power. The lack of electricity will also affect water supplies, since power is needed to operate water pumps.

Lt. Col. Peter Lerner, an Israeli military spokesman, did not comment on the explosion at the plant, but told The Associated Press that Israel's latest strikes signal "a gradual increase in the pressure" on Hamas.

Israel is "determined to strike this organization and relieve us of this threat," Lerner said.

International calls for an unconditional cease-fire have been mounting in recent days, as the extent of the destruction in Gaza became more apparent.

The house of the mayor of the Bureij in central Gaza was hit in an airstrike, and five bodies were pulled from the rubble, the Red Crescent said. Those killed included the mayor, 50-year-old Anas Abu Shamaleh, his 70-year-old father and three relatives.

In the southern town of Rafah, seven members of one family were killed in an airstrike and seven members of a second family were killed when tank shells hit their home, according to the Rafah office of the Palestinian Center for Human Rights, which keeps a casualty count.

In central Gaza, seven people, including five members of one family, were killed by tank shelling on a home, the Red Crescent said.

Tens of thousands of Gazans have been displaced by fighting in the border areas, which have come under heavy tank fire.

In the West Bank, Yasser Abed Rabbo, the secretary general of the Palestine Liberation Organization, called for a 24-hour cease-fire and said the offer was made after consultations with Hamas and the smaller Islamic Jihad group.

However, Izzat Rishq, a senior Hamas official in exile, said his group wanted to hear from Israel first.

Israeli government spokesman Mark Regev declined comment.

The largest group in the PLO is the Fatah movement of Palestinian President Mahmoud Abbas, Hamas' main political rival. Hamas is not a member.

Despite appeals for a cease-fire, both sides have been holding out for bigger gains.

Hamas has said it will not stop fighting until it wins international guarantees that a crippling border blockade of Gaza will be lifted. Israel and Egypt had imposed the closure after Hamas seized Gaza in 2007, defeating forces loyal to Abbas. Over the past year, Egypt has further tightened restrictions, shutting down hundreds of smuggling tunnels under the Egypt-Gaza border that had provide crucial tax income to Hamas. The closure of the tunnels drove Hamas into a severe financial crisis.

Israel has said it is defending its citizens against attack from Gaza by hitting Hamas rocket launchers, weapons storage sites and military tunnels under the Gaza-Israel border.

Israel said its troops will not leave Gaza until they have demolished the tunnels which have been used by Hamas to sneak into Israel to try to carry out attacks.

The military said Palestinian militants fired at least 64 rockets Tuesday at Israeli cities.

Meanwhile, the U.N. refugee agency for Palestinians said it found a cache of rockets hidden inside of one of its schools. It said the school was closed for the summer and was not being used as a shelter.

"We condemn the group or groups who endangered civilians by placing these munitions in our school", agency spokesman Chris Gunness said. "This is yet another flagrant violation of the neutrality of our premises."

It marked the third time since the Gaza war began that the U.N found weapons hidden in one of its schools.

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