JERUSALEM (AP) -- Israel said Thursday it has called up another 16,000 reservists, allowing it to potentially widen its Gaza offensive against the territory's Hamas rulers in a war that has killed more than 1,300 Palestinians and more than 50 Israelis.
The new call-up follows another day of intensive fighting, in which tank shells struck a UN school where Palestinians were sheltering and air strikes tore through a crowded Gaza shopping area. At least 116 Palestinians and three Israeli soldiers were killed Wednesday alone.
The move also coincides with stalled diplomatic efforts to end the war, which has claimed more than 1,360 Palestinian lives -- most of them civilians -- and reduced entire Gaza neighborhoods to rubble since it began on July 8.
Israeli attacks in the strip continued Thursday, with witnesses saying that munitions struck the Omar Ibn al-Khatab mosque next to a UN school in the northern town of Beit Lahiya.
Fifty-six Israeli soldiers and three civilians on the Israeli side have died in the Gaza campaign, as Palestinians have fired hundreds of rockets at Israel -- some reaching major cities -- and carried out attacks through tunnels beneath the heavily guarded frontier.
Israel has now called up a total of 86,000 reserves during the Gaza conflict, which it launched to try to end the rocket fire from Hamas and other militant groups in Gaza.
An initial aerial campaign was widened into a ground offensive on July 17. Since then the campaign has concentrated on destroying more than 30 cross-border tunnels that militants have constructed to carry out attacks on Israeli territory.
Israel says that most of the 32 tunnels it has uncovered have now been demolished and that getting rid of the remainder will take no more than a few days.
The strike in Beit Lahiya early toay damaged water tanks on the roof of a building near the mosque, sending shrapnel flying into the adjacent school compound."The shrapnel from the strike on the mosque hit people who were in the street and at the entrance of the school," said Sami Salebi, an area resident.
Gaza health official Ashraf al-Kidra said at least 15 people were wounded, with three of them in critical condition.
Kifah Rafati, 40, was being treated for shrapnel injuries at the nearby Kamal Adwan hospital. She said she and her six children had been sleeping in a classroom facing the mosque when the explosion went off. "There is no safety anywhere," she said.
On Wednesday Israeli tank shells struck a UN school in the Jebaliya refugee camp where some 3,300 Gazans had crammed in to seek refuge from the fighting, killing at least 17 people and drawing sharp condemnation from the United Nations.
Secretary-General Ban Ki-moon called the deadly school shelling "outrageous" and "unjustifiable," and demanded an immediate humanitarian cease-fire.
"Nothing is more shameful than attacking sleeping children," the UN chief said.
Hours later, an Israeli airstrike hit a crowded shopping area in the Shijaiyah district in Gaza City, killing at least 16 people, including local Palestinian photographer Rami Rayan, who was wearing a press vest at the time, and wounding more than 200 people, al-Kidra said.
Today marked a third day of particularly heavy Israeli air and artillery attacks, at a time when Egyptian cease-fire efforts appeared to have stalled. Israeli media said late Wednesday that Israel's Security Cabinet decided to press forward with the operation.
Egyptian officials, meanwhile, met with an Israeli envoy about Israel's conditions for a cease-fire, including disarming Hamas, according to a high-ranking Egyptian security official, who spoke on condition of anonymity because he was not allowed to discuss the delicate diplomatic efforts.
Hamas has said it will only halt fire once it receives guarantees that a seven-year-old Gaza border blockade by Israel and Egypt will be lifted.
Israel says it wants to decimate Hamas' rocket-launching capability, diminish its weapons arsenal and demolish the tunnels. It has launched more than 4,000 strikes against Hamas-linked targets, including rocket launchers and mosques where it says weapons were being stored.
Israeli strikes have also hit dozens of homes. Mahmoud Abu Rahma of the Palestinian human rights group Al Mezan said nearly half of the Palestinians killed so far died in their homes.
Israeli officials have said Hamas uses Gaza's civilians as human shields by firing rockets from crowded neighborhoods. Palestinian militants have fired more than 2,600 rockets at Israel over the past three weeks.
However, Pierre Kraehenbuehl, chief of the UN aid agency for Palestinian refugees, said Israel must try harder to ensure that civilians are not hurt, especially in Gaza, where 1.7 million people are squeezed into a small coastal territory. His agency has opened 80 of its schools to more than 200,000 Palestinians fleeing the violence.
"What maybe the world forgets ... is that the people of Gaza have nowhere to go," he said. "So when the fighting starts and they move, it is not as if they can cross a border to somewhere."
Barzak reported from Gaza City, Gaza Strip.